CHAPTER VI. SOME COMMON FLOWERS.

15. A TYPICAL FLOWER.

=I. The wallflower.=—After noticing the general habit of growth of a wallflower plant (Fig. 57), and especially the shape and venation of the leaves, make out the following parts in one of its flowers. On the top of the flower-stalk (called the _receptacle_) are:

(_a_) Four small, narrow, purplish leaves, called _sepals_. The four sepals together constitute the _calyx_. Take off the sepals one by one. Notice that two opposite sepals are bulged out at their bases, forming pouches containing nectar. Try to get out a small drop of nectar on the point of a pencil and taste it.

(_b_) Four showy leaves arranged in the form of a Maltese cross, called _petals_. They are yellow, or red, or purplish in colour, are delicately scented, and have beautiful velvety surfaces. The four petals together constitute the _corolla_. Take off the petals one by one.

(_c_) Six _stamens_, each consisting of a greenish stalk or _filament_ surmounted by a yellow, boat-shaped body, called the _anther_. The anther is a four-chambered box containing an enormous number of tiny yellow grains called _pollen grains_. Two of the stamens are shorter, and are fixed at a lower level on the receptacle than the remaining four. Take off the stamens one by one.

(_d_) A central _pistil_, shaped somewhat like a slender bottle. At the top, where the cork would come in a real bottle, is the notched _stigma_, slightly sticky. The neck is called the _style_, and the part corresponding to the body of the bottle is the _ovary_. Tear open the ovary with a needle to see the _ovules_, which in an undisturbed flower would have become seeds.

Watch bees visiting flowers. Does each bee confine itself to one kind (species) of flower at each journey, or does it visit several kinds indiscriminately? Try to discover what the bees are doing. Avoid alarming them.

=The work of flowers.=—The roots, stem, and leaves of a plant do a great deal of work, but, as it is performed for the benefit of the plant itself, it is all, in a sense, selfish work. Plants, however, like animals, grow old in time, and at last die. If they are not to become extinct it is evident that they must devote part of their energies to producing new individuals, and to sending these forth into the world as well equipped as possible for the battle of life. This unselfish and self-sacrificing part of a plant’s life-work is called =reproduction=; in the higher plants it is carried out by flowers.

=The structure of a wallflower blossom.=—The flowers of different groups of plants vary greatly in structure, but a good general idea of the arrangement of the parts of a flower can be obtained by examining the blossoms of a wallflower plant (Fig. 58). Other flowers may afterwards be compared and contrasted.

There are evidently at least eight leaves in the flower, but, unlike the green foliage leaves, these are not arranged spirally, but stand at nearly the same level on the end—called the =receptacle=—of the flower-stalk. The most external leaves are four in number, small, narrow, and purplish in colour. Each of these leaves is called a =sepal=, and the four sepals together constitute the =calyx= of the flower. Two opposite sepals are pouched at the base, forming pockets, in which a sugary fluid, called nectar, collects. Before the bud opens, the calyx is the only part of the flower which is visible. It is probably developed in the wallflower solely for the protection of the more delicate structures within. Next, inside the sepals, placed alternately with them, and standing a little higher on the receptacle, are four showy leaves arranged in the form of a Maltese cross. These leaves are called =petals=, and the four petals together form the =corolla=. The petals are delicately scented, and their surfaces have a beautiful velvety sheen.

When the sepals and petals are removed, there remain standing on the receptacle six =stamens= surrounding a centrally-placed =pistil= (Fig. 58, D). The stamens are the male part, and the pistil is the female part, of the flower. Each stamen consists of a greenish stalk or =filament=, surmounted by a yellow boat-shaped body called the =anther=. The anther is a box with four compartments (Fig. 59). When it is ripe, each compartment contains an enormous number of tiny, yellow grains called =pollen grains=; and when the anther bursts (as it does as soon as the flower opens) its inner face is covered by the yellow dust of the pollen.

The =pistil= bears a rough resemblance to a slender bottle, and consists of three distinct parts. The neck of the “bottle,” called the =style=, is short in the wallflower, and differs from an ordinary bottle-neck in being solid instead of tubular. At the top of the neck, where the cork would come in a real bottle, is a body called the =stigma=. The stigma of the wallflower pistil is hairy, notched, and slightly sticky, from the presence of a sugary solution which forms upon it. The part of the pistil, corresponding to the body of the bottle, is the =ovary=. It contains four rows of little white =ovules=, which are destined to become seeds capable of growing up and forming new wallflower plants.

The relations of the parts of the flower are well seen in Fig. 59.

=Fertilisation.=—In order that an ovule may become a seed, its contents must mix with the contents of a pollen grain. The fusion of the two constitutes =fertilisation=. For fertilisation to take place, the pollen grain must first of all gain access to the stigma of the pistil. If this be prevented the flowers will wither without forming ripe seeds. (This may be proved easily by Expts. =18=, 3 and =21=, 2.) The sugary solution at the top of the stigma stimulates the pollen grains to growth, and each puts out a long tube which grows down the style. The living matter of the grains keeps near the tips of the tubes as these continue their journey down the style. At length the tubes enter the ovary and find the ovules. Each ovule has at one end a minute pore (the micropyle—p. 6), and a pollen tube finds this and enters it. The living matter of the pollen tube fuses with that of the ovule in the neighbourhood of the pore, and fertilisation is effected. It is now easy to understand that the comparatively insignificant stamens and pistil are the all-important parts of a flower.

=How the wallflower advertises.=—Botanists have proved that a flower produces more, and also better, seeds when it is fertilised by pollen from another flower of the same species. This is called =cross fertilisation=. The wallflower relies upon bees for the transference of the pollen from one flower to another; and it is solely to attract them that the petals are so delicately scented and brilliantly coloured, and that sweet nectar collects in the sepal-pouches. The gaily coloured petals are therefore advertisement placards which are hung out to attract the attention of bees. A bee comes to a wallflower for the sake of both nectar and pollen—the “bee-bread.” As the bee thrusts its proboscis down between stamens and pistil in search of the sweet liquid in the pouches, its head is pretty certain to come in contact with, and to brush off, some of the pollen dust hanging loose on the inner faces of the anthers. When the bee flies off to another wallflower and continues its search for nectar, it almost invariably leaves some of the pollen, from the first flower, on the hairy and sticky stigma of the second.

In almost all cases when a flower is brightly coloured it depends upon the help of insects for cross fertilisation.

16. THE WALLFLOWER FAMILY.

1. =Shepherd’s purse.=—Compare the shepherd’s purse (Fig. 60) with the wallflower. The flower is very much smaller, and white, but the parts have the same arrangement as in the wallflower, viz., four sepals, four petals arranged in the form of a cross, six stamens (two short and four long), and a central pistil, all arranged separately on the receptacle. Look down the plant, and notice that in the oldest (lowest) flowers, everything but the pistil has dropped off, and that this has become greatly enlarged to form a _fruit_. Cut some fruits open, both lengthwise and crosswise, and observe that each consists of two pocket-like chambers, separated by a thin partition on which the seeds are borne. Notice the manner in which the oldest fruits have opened naturally.

2. =Other relatives of the wallflower.=—Compare also the flowers and fruits of the stock and candytuft, and also cress, mustard, radish (Fig. 61), cabbage, and turnip, which have been allowed to “run to seed.” Examine the roots of the turnip and radish.

Make a note of the earliest dates on which you see the above plants in flower.

=The wallflower family.=—The plants of the family to which the wallflower belongs are of very great importance to mankind; for while not one of them is poisonous, many are extremely valuable as food-crops. They are all _dicotyledons_; that is, their seeds contain two cotyledons or “makeshift leaves,” as has already (Chapter I.) been seen in the case of the mustard. The net-like venation of the leaves of the full-grown plant also indicates this. There is a great family likeness between the flowers of this group, and they are easily recognised (Fig. 61 _a_, _c_) by the cross-shaped corolla and the six stamens (two short and four long). All the parts of the flower—sepals, petals, stamens, and pistil—are fixed separately on the top of the flower stalk or receptacle. The cross-arrangement of the petals has led to these plants being called =Crucifers= (cross-bearers). The =shepherd’s purse= (Fig. 60)—so-called from the shape of its fruit—is a common weed with small, white flowers. All stages of the flower may generally be found on the same plant. While at the top the buds may still be unopened, the flowers below have been fertilised (in this case generally self-fertilised); the sepals, petals, and stamens—having fulfilled their duties—have fallen off; the ovules have become seeds, and the ovule-box or ovary has become a seed-box or fruit, consisting of two bags separated by a partition which bears two rows of seeds on each side (Fig. 62).

=Useful crucifers.=—The turnip and the radish are largely cultivated for their roots (Figs. 63 and 64), and are then taken out of the ground at the end of their first season. As these plants naturally flower in their second year of growth and then die, they are called =biennials=. The production of flowers and fruit is a great strain on a plant, and it is to prepare for the effort that the turnip and radish store so much food in their roots during the first year as to give them a globular and spindle shape respectively. A carrot is not a crucifer, but it also adopts this device.

The cabbage is grown for its leaves. Varieties of the cabbage are Brussels sprouts, broccoli, and cauliflower; it is the very small flower-buds of the last two which are eaten. Cress and white mustard are eaten in the seedling stage. The seeds of the black mustard are ground and eaten as a condiment.

17. THE BUTTERCUP FAMILY.

1. =The buttercup.=—Notice the habit of growth, characters of the leaves, etc. Is the buttercup a dicotyledon? Make this observation with all flowering plants. (See, however, Chap. VIII., p. 163.)

In the flowers of a buttercup (Fig. 65) make out:

(_a_) The _calyx_ of five green, separate sepals; they are the only parts to be seen in young, unopened buds. Take off the sepals of a fully-opened flower one by one.

(_b_) The _corolla_ of five, golden-yellow, separate petals, alternate with the sepals. Notice the nectary—a little pocket—near the base of the upper surface of each petal. Take off the petals one by one and observe that they are fixed on the receptacle, a little higher than the sepals.

(_c_) The large number of separate _stamens_, inserted still higher on the receptacle.

(_d_) On the top of the receptacle the large number of separate, flask-shaped bodies, which together make up the _pistil_. Each of these is called a _carpel_.

Watch bees and other insects visiting buttercups and notice how they stand on the flower to obtain the nectar from the nectaries. Does a bee on leaving go to another buttercup, or does it change to another kind of flower?

In a flower from which the sepals, petals, and stamens have fallen, notice the compound _fruit_ (Fig. 66), consisting of ripened carpels. Open a carpel with a needle and pick out the single seed.

2. =Other plants of the buttercup family.=—Notice that in the anemone (Fig. 67) and marsh marigold (Fig. 68), the sepals appear to be absent (the three leaves under the anemone flower are not parts of the flower; they are called _bracts_). The apparent petals are really the sepals; it is the corolla which is absent. Observe the large number of stamens, and notice that the pistil consists of several separate carpels.

In what kind of ground have you seen these plants growing wild?

=The buttercup family.=—The buttercup (Fig. 65) and its relatives resemble the crucifers (1) in being dicotyledons (as is indicated (p. 40) by the venation of the leaves), and (2) in the fact that, of the parts which compose the flower, each group is arranged separately on the receptacle. For example, the stamens are not connected with either the calyx, the corolla or the pistil. Having noted these points of resemblance, however, we are met by some important differences. In the buttercup there are usually five sepals and five petals; there may be twenty or more stamens; and the pistil is not a single structure, but consists of a number of separate parts, each of which is called a =carpel=, and contains a single ovule. The pistil of a crucifer consists of only two carpels; these are welded together into a single structure, and until the fruit ripens a slight notch in the stigma is the only external indication that the pistil is in two parts.

Insects visit buttercups for the sake of nectar and pollen, and whilst creeping about the flower transfer pollen to the stigmas of the carpels. The insects may have brought some of this pollen from other flowers, and then cross-fertilisation is caused. If the pollen is derived from the same flower self-fertilisation is the result.

After fertilisation the ovules become seeds; the sepals, petals, and stamens drop off; and the carpels swell up, forming a dry compound fruit (Fig. 66), consisting of several nutlets.

Two other common plants of this family are the =anemone= (Fig. 67) and =marsh marigold= (Fig. 68). In neither of these cases has the flower any petals, but the calyx has taken on the appearance of a corolla. In the marsh marigold it is large and yellow; in the anemone it is white or purple. The three green leaves immediately beneath the flower of the anemone are called _bracts_. They should not be mistaken for sepals.

The plants of the buttercup family are as generally poisonous as the crucifers are wholesome. Monkshood is especially poisonous, and its root has been mistaken, with fatal results, for that of horse-radish. It is often noticed that grazing cattle avoid the buttercups in a field. The bitter and disagreeable taste of the leaves is of course a valuable protection to the plant.

18. THE PEA FAMILY.

1. =The garden pea.=—Notice again the habit of the plant: its compound, net-veined leaves with large stipules, and its method of climbing by tendrils which are modified leaflets. Examine the flower and make out (_a_) the _calyx_ of five united sepals; (_b_) the curiously shaped _corolla_. The large upper petal is called the _standard_, the two at the side are the _wings_, and the lowest (really two locked together) is the _keel_; (_c_) the ten _stamens_. One (opposite the standard) is separate; the remaining nine have the lower parts of their filaments united to form a tube. Slit open the filament-tube and remove the stamens, noticing how they are attached to the other parts of the flower; (_d_) the _pistil_. Slit open the ovary and see the ovules in it. Watch the various stages of the formation of the fruit (pod).

Watch bees visiting the flowers. The insect alights on the wings, and its weight pulls them down and lowers the keel, bringing the stamens against the bee’s body.

Cut a complete flower down the middle with a sharp knife, and notice that calyx, corolla, and stamens seem not to be inserted separately on the receptacle, but to spring from a common base.

2. =Other plants of the pea family.=—Examine also bean, vetch (Fig. 69), meadow vetchling (Fig. 70), clover (Fig. 71), laburnum (Fig. 73), and broom. Compare the habits of growth of the plants, and notice that they all have the same peculiar shape of flower. Dissect a flower of each. Notice that in laburnum and broom the ten stamens are all united. In clover the flowers are in _heads_. Notice how the leaflets of the clover plant close at sunset.

3. =Fertilisation.=—Dig up several red clover plants in early summer and pot them. Cover about half the plants with gauze, so fixed on wire frames that insects cannot get inside, and then put all the plants together where they will get plenty of sun. Water them regularly, and notice which plants ripen seed. How do you account for the differences?

=The pea family.=—Plants of the pea family are found in all quarters of the earth. They are of very diverse size and habit of growth; the laburnum, for example, is a tree; the gorse is a bush; the broad bean has a strong, erect, herbaceous stem; the pea is a weak-stemmed climbing plant; the clovers are small herbs with flowers forming “heads.” Most of the members of the family agree in having a “butterfly-shaped” corolla (Figs. 72 and 73), which consists of three well-marked parts, viz., a large =standard=, a pair of =wings=, and two closely-connected petals which form a boat-shaped =keel=. There are ten stamens, and the filaments of nine of these usually cohere to form a tube surrounding the ovary. In the laburnum, gorse, and a few others, all the ten stamens are united. When a bee visits the flower, in search of nectar, it alights on the “wings” of the flower, and its weight depresses these and pulls down the keel. The anthers of the stamens are so placed with respect to the keel that this results in a mass of pollen being scraped off the anthers and forced out at the beak of the keel, or in the stamens being suddenly liberated and scattering pollen on the bee. The pollen sticks to the bee’s body, and some of it is almost certainly transferred to the stigma of the next flower visited. The quaint shape of the corolla is thus definitely adapted to the visits of insects; for the nectar is so placed that to obtain it the insect must carry off some of the pollen.

The calyx, corolla, and stamens are not obviously—as in the wallflower and buttercup—inserted separately on the receptacle, but seem to spring from a common base.

The fruit is a =pod= (Fig. 3), which opens when ripe along both margins and liberates the seeds. Laburnum seeds are poisonous, but the seeds of many other plants of the family (peas, beans, lentils, etc.) are valuable foods.

19. THE ROSE FAMILY.

1. =The wild rose= (Fig. 75).—With a sharp knife cut vertically through the middle of a wild rose. Notice that the receptacle forms a deep cup, and that the carpels of the pistil are enclosed in the cup. From the edge of the cup spring the five sepals, five petals, and numerous stamens. What is the great difference between a rose and a buttercup?

Trace the formation of the succulent fruit or hip from the receptacle cup of the flower. Cut through a rose hip, and observe the ripened carpels in the interior.

2. =The blackberry.=—Similarly examine a blackberry flower (Fig. 76). This is still more like a buttercup, but—as in the rose and the pea—the calyx, corolla, and stamens seem to spring from a common base, and not to be inserted separately on the receptacle.

Trace the formation of the compound fruit, and notice that each part is like a little plum or cherry.

3. =The cherry.=—Similarly examine cherry blossom (Fig. 77). The pistil consists of one carpel, and is fixed at the bottom of the receptacle-cup, while the calyx, corolla, and stamens are fixed on the margin of the cup. Trace the origin of each part of the fruit.

Compare the plum and apricot.

4. =The apple and pear.=—Cut vertically through an apple blossom (Fig. 74) or pear blossom (Fig. 78), and notice that the ovary is embedded in the receptacle, and that calyx, corolla, and stamens are fixed on the top of this. Cut across the ovary and see the five divisions (carpels).

The eatable part of the fruit is the swollen receptacle. Compare the hawthorn.

=The wild rose.=—The plants of the rose family are, most commonly, woody trees or shrubs. The leaves are provided with stipules in nearly all cases. The =wild rose= (Fig. 75) may be taken as a type of the group. It bears a superficial resemblance to a buttercup, but on dissection considerable difference in the arrangement of the parts is seen. In the rose, the receptacle is urn-shaped; from the margin of the urn spring the five sepals, five petals, and numerous stamens; while inside the urn the separate carpels of the pistil are inserted. In the =blackberry= (Fig. 76), =raspberry=, and =strawberry= the receptacle is knob-shaped, and the carpels are arranged on the outside of the knob, somewhat as in the buttercup. Here again, however, the calyx, corolla, and stamens differ from those of the buttercup in seeming to arise from a common base.

The differences between the rose, blackberry, raspberry, and strawberry are more marked when the pistil has become a fruit. The fleshy part of the rose hip is the urn-shaped receptacle which encloses the ripened carpels. In the case of the blackberry and raspberry the receptacle is dry, and is surrounded by the compound fruit (Fig. 76, 3) of the several bodies like little plums or cherries. The eatable part of the strawberry fruit (Fig. 144) is the swollen receptacle, on the outside of which are the little yellow nutlets derived from the carpels of the flower.

In the =cherry= (Fig. 77), =plum=, and =apricot= the pistil consists of only one carpel, which is enclosed in the urn-like receptacle. After fertilisation, the greater part of the wall of the ovary becomes fleshy, and one of the two ovules contained in it becomes a seed. The “stone” is formed from the innermost part of the ovary wall.

The =apple= (Fig. 74) and =pear= (Fig. 78) have their five carpels embedded in the receptacle, and the rest of the flower stands on this part. The eatable portion of the fruit is the swollen receptacle. The =hawthorn= has usually only two carpels, and in the fruit the part derived from the receptacle becomes hard and horny. In other respects it is very similar to the apple.

The rose family is widely distributed, especially in temperate regions.

20. THE PARSLEY FAMILY.

1. =The poison hemlock.=—Examine this plant (Fig. 79) very carefully, remembering that it is poisonous. Notice the general habit of growth; the characters of the sheathing, compound leaves; the hollow ribbed stem; and also the arrangement of the flowers, which is characteristic of the family. From the top of a main flower-stalk several smaller stalks come off together, like the ribs of an umbrella. From the top of each of these spring the stalklets which bear the small white flowers. Notice the _bracts_ at the points of origin of the stalks. Examine the flowers, and watch insects visiting them. Which insects are most commonly found on the flowers?

Compare the cow parsnip, the water hemlock, carrot, parsley, parsnip, and celery, carefully noting the points of resemblance and difference.

=The parsley family.=—The plants of this family may be recognised easily by the arrangement of the flowers. Several stalks spring together from the top of the main flower stalk and each of these again gives rise at its tip to a number of smaller stalks, at the ends of which the small flowers are borne (Figs. 79 and 80). The flowers are fertilised by the aid of insects, and as the nectar is on the surface it is accessible to small insects such as flies, beetles, etc. The flowers are rendered more conspicuous by being placed close together. The stems are usually hollow, and the leaves are alternate, and generally compound, with sheathing bases. Many of the plants of this family are very poisonous, and such should be carefully distinguished and whenever possible exterminated.

The =poison hemlock= (Fig. 79) varies in height from two to seven feet. It has a hollow stem which is spotted with purple in the lower part, and when bruised the leaves give off a smell like that of mice. Cattle are often poisoned by eating the plant in hay, and children have been poisoned even by blowing whistles made from the stem. The =water-hemlock= is extremely poisonous. It grows along the sides of pools. The stem is hollow, and the leaflets of the compound leaves are finely toothed. The root is a cluster of fleshy swellings, and has unfortunately a rather pleasant taste. Other poisonous plants of the family are the =water dropwort= and the =fool’s-parsley=. Among the harmless and useful members of the group are =celery= (when cultivated), =carrot=, =parsnip=, and =parsley=.

21. THE PRIMROSE AND COWSLIP.

1. =The primrose.=—Examine the habit (Fig. 81) of the plant, its underground stem, its spoon-shaped leaves—arranged in a rosette—and the manner in which the flowers spring from the stem. In the flower make out (_a_) the _calyx_, 5-pointed and with united sepals; (_b_) the _corolla_, consisting of 5 petals united below into a tube. Tear down the corolla-tube to see (_c_) the 5 _stamens_ inserted on the corolla-tube. In some (“thrum-eyed”) flowers the anthers are at the top of the tube; in others (“pin-eyed”), they are halfway down; (_d_) the _pistil_, consisting of stigma, style, and ovary. In thrum-eyed flowers the style is short and the stigma is halfway down the corolla-tube; while in pin-eyed flowers the style is long and the stigma is at the top of the tube. Do you find both pin-eyed and thrum-eyed flowers on the same plant, or does one plant bear only one kind?

2. =Fertilisation.=—Cover up a plant of each kind with gauze, to keep insects from the flowers, and notice whether the covered flowers ripen seeds like the others.

3. =The cowslip.=—Compare the cowslip (Fig. 83), and notice that the main stalk gives off from the same point several smaller stalks, each of which bears a flower. Observe that the cowslip also has both pin-eyed and thrum-eyed forms of flowers.

=The primrose and cowslip.=—In the primrose we have flowers of a type differing from all those previously considered in this chapter. Not only are the sepals joined together to form a five-toothed =calyx-tube=, but the five petals are also joined together to form a =corolla-tube=, and the stamens are fixed on the corolla-tube. There are two kinds of primroses, known to country children as pin-eyed and thrum-eyed flowers respectively (Fig. 82). The two forms grow on separate plants. In a pin-eyed primrose the style is long, and the stigma—looking somewhat like the head of a pin—is at the top of the corolla-tube; while the stamens are halfway down. The thrum-eyed primroses have their stamens at the top, while the stigma of the pistil is halfway down the tube, exactly opposite the place where, in the pin-eyed form, the stamens are inserted. This curious state of things was a great puzzle to botanists until Darwin cleared up the mystery. A bee, thrusting its proboscis down a pin-eyed primrose in search of the nectar at the bottom, dusts it with pollen about halfway down—just in the place which will come in contact with the stigma when the animal visits a thrum-eyed flower. And the pollen from the thrum-eyed form adheres to the part of the bee which will presently touch the stigma of a long-styled flower. This beautiful and simple arrangement makes it practically certain that each primrose shall be fertilised by pollen from the other form. In the thrum-eyed form, however, it is possible for pollen to fall upon the stigma and produce self-fertilisation.

It is obvious that the cowslip (Fig. 83) is closely related to the primrose. The difference lies chiefly in the character of the flower-stalk. In the cowslip this is long, and it bears at its top several stalklets, each of which ends in a flower. As in the primrose, cross-fertilisation is secured by some flowers being pin-eyed (long styled) and others thrum-eyed (short styled).

22. THE DAISY AND ITS RELATIVES.

1. =The daisy.=—Take up several daisy plants (Fig. 84) entire, and wash away the soil from the roots. Notice how the stems—some of which are underground—are connected together. Draw a leaf. What advantage is it to the plant to have leaves of the shape noticed? Cut vertically through the “head,” and notice that what is usually called the “flower” really consists of a large number of small flowers.

The central or _disc flowers_ are tubular. Which disc flowers open first, those near the middle or those nearer the edge of the disc? Pick off a flower and notice the 5-toothed corolla. Tear the corolla down with a needle, and observe the tiny stamens (5) fixed on the corolla-tube. The anthers are joined together. Notice the divided stigma of the pistil. The white and pink _ray flowers_ have strap-shaped corollas. They have no stamens, but each has a pistil like that of a disc flower. What do you think is the object of the ray flowers being so conspicuous? Why do they close over the disc at night?

Notice the large number of green _bracts_ below the disc.

2. =The dandelion.=—Compare the dandelion (Fig. 85). Notice that all the flowers are strap-shaped, like the ray flowers of the daisy. Pull one out, and make out the strap-like corolla, the five stamens with joined anthers, and the double stigma (Fig. 86, 2). Notice the tuft of fine hairs below the corolla and above the knob-like ovary. The tuft of hairs is the top of the calyx-tube.

When the flowers have been fertilised, the yellow corollas wither, and each calyx-tube elongates until it is about an inch long, the tuft of fine hairs being still at the top (4). Blow a “clock,” and notice how easily the fruits are detached from the disc and how slowly they settle. What advantage is this to the plant?

3. =The thistle.=—Compare the thistle (Fig. 87). The bracts are very prickly. Is this an advantage? Are the flowers tubular or strap-shaped? Examine the fruits (“thistle down”) and compare with those of dandelion.

=The daisy.=—What is generally called the “flower” of the daisy (Fig. 84) really consists of a very large number of small separate flowers set close together on a flattened disc or receptacle. The group of flowers is called a =head=. On the lower surface of the head are several green leaves, or bracts, which protect the bud before it opens. The flowers of a daisy-head are of two kinds. The white or pink straps set round the edge of the head are the corollas of the ray flowers. They have no stamens, but a pistil with a divided stigma is present in each. The disc flowers are yellow and tubular. The corolla consists of five united petals. On it are fixed five stamens, the anthers of which are joined together. The pistil is like that of a ray flower. No calyx is present in either the ray or disc flowers of the daisy.

The daisy is fertilised by the aid of insects which are attracted by the strap-like corollas of the ray flowers.

The =dandelion= “flower” (Fig. 85) is also really a head consisting of a great many separate flowers. There are often between two and three hundred of these little flowers present in one head. Below the head are several green bracts, and these protect the flowers both in the bud and at night (Fig. 86). The flowers of the dandelion are all of one type. The corolla is strap-shaped (Fig. 86, 2), and of a beautiful yellow colour to attract insects. On the end of the strap may be seen five small teeth which indicate that it really consists of five united petals. At the base of the corolla is a tuft of fine hairs, which is the top of the calyx-tube, and at the bottom of the flower is a little white knob—the ovary. The five stamens are fixed on the inside of the corolla tube. Their anthers are united to form a tube through which the upper part of the style, and the forked stigma protrude.

It will be noticed that a dandelion flower is practically like a ray flower of a daisy, with the addition of calyx and stamens.

The =thistle= (Fig. 87) is another common member of the family. Its bracts are prickly, and are a protection from the attacks of animals. The flowers (Fig. 88) are all tubular. The common thistle distributes its fruit by a plume of radiating fine hairs—the calyx. The fruit is commonly known as “thistle down.”

The =Compositae=, as plants of this family are called, are found in all parts of the world. The family is the largest in the vegetable kingdom, and many of the plants included in it are of considerable importance.

23. THE FOXGLOVE FAMILY.

1. =The foxglove.=—Examine a flowering plant of foxglove (Fig. 89). Notice the general habit of growth. In the flower make out the five-lobed calyx, the irregular corolla with five petals joined to form a tube, the four stamens (two long and two short) fixed on the corolla tube (Fig. 90), and the form and attachment of the pistil. Watch bees visiting the flower. 2. =The speedwell.=—Compare the speedwell (Fig. 91), and notice that the corolla is more nearly regular than is the case with the foxglove, that it consists of _four_ combined petals, and that _two_ stamens are fixed upon it.

3. =The musk.=—Compare the musk. Dissect a flower and notice the forms and positions of the parts. Especially examine the pistil with its two-lobed stigma. With a hair, carefully touch one of the lobes of the stigma of a growing flower and watch how the lobes close. Do the lobes open again? Put a little pollen on, and watch to see if this time the lobes open again after closing.

Watch insects visiting the flowers and try to make out how the pollination of the stigmas is brought about.

=The foxglove family.=—In the primrose and the disc-flowers of the daisy are seen examples of regular, dicotyledonous flowers with five petals fused to form a corolla-tube, and with five stamens inserted on the corolla. In the strap-shaped flowers of the dandelion the corolla is irregular, but still consists of five fused petals and bears the five stamens.

The =foxglove= (Fig. 89) and its relatives have also irregular corollas of joined petals on which the stamens are fixed; but the stamens are usually only four in number, two being long and two short as in Fig. 90, _b_. In the foxglove the stamens ripen and shed their pollen before the pistil of the same flower is mature. This prevents self-fertilisation, but bumble bees in passing from one flower to another convey the ripe pollen of the younger flowers to the stigmas of flowers which are ready for fertilisation.

The pretty blue =speedwell= (Fig. 91) is closely related to the foxglove, but its corolla has only four lobes instead of five, and some times these seem of almost equal size at the first glance. Generally, however, the corolla is very plainly irregular. The speedwell has only two stamens, while =mullein= has five.

=Calceolaria=, =musk=, =gloxinia=, and =snapdragon=—other members of the family—are often cultivated in gardens.

The flowers of the musk are especially interesting, because they show so well what is called =irritability=,—the power which all living things possess of acting in a definite manner in response to a definite irritation or stimulus. We have already seen good examples of plant-irritability in the way a climbing stem winds itself round a support. The stigma of the musk flower has two flaps. If these are touched with a hair or bristle they quickly close together, but presently open again as if they had found out that they had been tricked. When, however, a little pollen is put on the flaps they close finally, for their whole object is accomplished.

Some of the plants in this family are poisonous, the foxglove being especially so in all its parts.

24. THE LABIATES.

1. =The deadnettle.=—Examine a deadnettle plant (Fig. 92). Notice the habit of growth, and write down a description of the shape and appearance of the stem and leaves. What is the shape of the flower? How many sepals, petals, and stamens has it? Do the stamens ripen first, or does the pistil? What insects do you find visiting the flower? Try to find out how they pollinate the stigma.

2. =Other labiates.=—Compare the sage (especially in respect of its relation to bees), rosemary, thyme, marjoram, and mint, and distinguish between their various flowers, leaves, and scents.

=The labiates.=—The deadnettle is a type of an easily recognisable family of plants. The stem is square in section, and the leaves are arranged upon it in opposite pairs at right angles to each other. The plants are hairy and have distinctive odours. The aroma of =thyme=, =mint=, =marjoram=, =sage=, etc., has led to the plants being used for flavouring food. None of the labiates is poisonous.

The shape of the flower is very characteristic, and is specially adapted to the visits of bees. The flowers are so modified that the lowest part of the corolla forms a platform on which the bee may conveniently alight, while the upper petals unite into an arched roof which protects the pistil and stamens.

The mechanism of cross-pollination is particularly well shown in the case of the =sage= (Fig. 93). The flower contains four stamens, but two of these have lost their use, and the others are modified in a strange manner. The whole stamen has somewhat the shape of a capital T, and at each end of the cross-piece is a pollen box. Usually the cross-piece (_c_, Fig. 93, 3) is not at right angles to the filament, but is swung up—the junction acts as a hinge—until it is nearly vertical (Fig. 93, 4). The pollen box _s_, which is at the lower end of the cross-piece _c_ when this is vertical, contains hardly any pollen. The entrance to the honey tube is thus guarded by two pillars, the filaments (_f_) of the stamens; and the lower pollen box (_s_) of the cross-piece of each stamen is directly in front of the bee’s head as it stands on the lower lip of the flower. When it pushes forward its head to reach the nectar it comes in contact with the lower pollen boxes, and the cross pieces swing round on their hinges, bringing the upper pollen boxes down with a smack on the bee’s back (Fig. 93, 1), and sprinkling it liberally with pollen dust. Having shed their pollen the stamens shrivel up, and the pistil comes to maturity. As the pistil ripens, the stigma arches over (Fig. 93, 2) so as to scrape along the back of any bee visiting the flower for the nectar, and thus to wipe off the pollen which has been brought from a younger flower.

25. THE LILY AND SNOWDROP FAMILIES.

1. =The hyacinth.=—Take up a plant (Fig. 94) entire and notice the underground bulb with roots springing from its lower surface, and the long narrow leaves. Is the venation of the leaves parallel or net-like? Is the hyacinth a monocotyledon or a dicotyledon? See the bract at the base of each flower-stalklet.

Examine the flower. Its leaves cannot be distinguished into calyx and corolla, but are quite similar to each other in size, shape, and colour. They are therefore called the _perianth_. The perianth leaves are united to form a tube. Tear down the tube to see the six stamens fixed on it. Are they all on the same level? Examine the pistil and cut the ovary across to see the ovules in the three joined carpels. Which is fixed at the higher level, the perianth or the base of the pistil?

2. =Other plants of the lily family.=—Examine also the white lily, tulip, star of Bethlehem, and lily of the valley, and notice that in spite of small differences they are all monocotyledons (how do you know this?) and all have the _perianth fixed below the ovary_.

3. =The snowdrop.=—Compare and contrast the snowdrop (Fig. 95). Make out that it is a monocotyledon, but that its _perianth is inserted above the ovary_. This is the great point of difference from the lily family. Notice also how the stamens are fixed.

4. =Other plants of the snowdrop family.=—Examine the daffodil (Figs. 55 and 96) and narcissus. Arising from the short perianth tube of the daffodil is a longer one which is often mistaken for a corolla; it is called the _corona_. None of the flowers hitherto described contains anything corresponding to a corona. The corona in the narcissus is short. As in the snowdrop, the perianth is fixed _above_ the ovary. Observe how the stamens are fixed, and notice the dry leaf beneath the flower.

=The lily family.=—Either the =wild hyacinth= (Fig. 94) or the cultivated single hyacinth may be taken as a good representative of this family. The first point which strikes the student on examining the general “habit” of the plant is the character of the long sheathing leaves. Their veins do not form an obvious network, such as is seen in the leaves of dicotyledons, but run lengthwise and roughly parallel to each other in the manner characteristic of grasses and other monocotyledons (p. 40). The leaves are narrow, and are not divided into blade and stalk; they and the flower stalk spring from an underground bulb (p. 84) which consists chiefly of the swollen leaf-bases of a previous season. A separate calyx and corolla are not to be distinguished in the flower; the six leaves being all alike in size, shape, and colour. These six leaves hence receive a special name, and are called the =perianth=. The perianth leaves are united into a tube, on the inside of which the six stamens are arranged in two series of three each. In the middle of the flower, and fixed _above the insertion of the perianth_, is the pistil, which consists of three united carpels.

It will be noticed that the parts of the flower are in threes. There are six united perianth leaves (three inner and three outer), six stamens (also in two series), and three united carpels. This is very common—though by no means universal—in monocotyledons.

All the plants of the lily family—including the tulips, the true lilies, lily of the valley, asparagus, onion, etc.—agree in being monocotyledons, and in their flowers having a conspicuous perianth (for attracting insects) and six stamens, and in the ovary being above the insertion of the perianth.

=The snowdrop family.=—Plants of this family are very similar to those of the lily family; in fact in only one respect can any sharp line of demarcation be drawn between the two groups; in the snowdrop and its relatives the other parts of the flower stand _upon the ovary_ (Fig. 96). The flowers of some plants of the family, _e.g._ the daffodil, possess a tubular outgrowth of the perianth, which is called a =corona=. It is often mistaken for a corolla.

26. THE ARUM LILY.

1. =The cuckoo-pint.=—Examine the habit of the plant, and then cut open the “flower.” You will probably find a number of small flies inside. Examine the central rod and make out the stamens and pistils on it. Which ripen first?

=The arum= “=lily=,” with its humble relative the cuckoo-pint (Fig. 97), merits special mention; for, in the first place, it is not a lily at all, and secondly, it furnishes an extremely interesting example of pistils coming to maturity before anthers, which is rather rare.

What is generally called the “flower” of the cuckoo-pint, or “lords and ladies,” consists of a big curled leaf with a purple rod sticking up in the middle. Near the bottom of the rod, but hidden from sight by the lower part of the leaf, the true flowers arise. The chamber containing them is shut in by a series of stiffish hairs which point downwards. Below the hairs the rod supports a series of anthers and, near the bottom of the chamber, several pistils. On cutting open the chamber one nearly always finds a number of small flies, covered with pollen, which they have brought from another arum. The flies get in easily enough, but once in they are prisoners, for the down-pointing hairs prevent them from getting out again. The pistils near the bottom of the rod ripen, and are fertilised by the pollen the flies have brought. After a time the anthers above ripen and shed their welcome pollen on the hungry captives. Soon after this the hairs at the top of the chamber shrivel up, and the flies, once more covered with pollen, are at liberty to return to the outer world and, untaught by experience, to repeat the experiment on another “flower.”

EXERCISES ON CHAPTER VI.

1. Describe the arrangement of the stamens in the wallflower, the sage, and the primrose.

2. Describe the pistil of the deadnettle, the primrose, and the shepherd’s purse. (1895)

3. In what respects does the flower of the buttercup differ from that of the wild rose?

4. Explain the arrangement and form of the stamens in some flower selected by yourself. Describe the structure and contents of the anther. (1897)

5. Where is the pollen of a flower formed? What is its use? (1898)

6. Name one or two plants which do not ripen seed if insects are excluded, and show why they do not. (1898)

7. Name two plants which would be in flower in each of the months from March to August inclusive, and state in what localities they would be found? (N.F.U.)

8. In what ways are insects attracted to visit flowers? Give examples, with an explanation and drawing in each case, of any special structure which may be a means of attraction. (N.F.U.)

9. Name ten flowering plants which may be found, (_a_) in a shady wood, (_b_) in a meadow, in late spring.

10. Name any fresh specimens of flowers which usually could be obtained growing wild in March, June, and October respectively. (N.F.U.)

11. What wild flowers would you expect to find in early April in your part of the country? In what kinds of places would you look for them? (N.F.U.)

12. Name the parts of any flower you have examined which are concerned with the production of seed. (King’s Scholarship, 1904)