CHAPTER XVIII.

CLASSIFICATION OF DICOTYLEDONS.

DIVISION I.--_Choripetalæ_.

Nearly all of the dicotyledons may be placed in one of two great divisions distinguished by the character of the petals. In the first group, called _Choripetalæ_, the petals are separate, or in some degenerate forms entirely absent. As familiar examples of this group, we may select the buttercup, rose, pink, and many others.

The second group (_Sympetalæ_ or _Gamopetalæ_) comprises those dicotyledons whose flowers have the petals more or less completely united into a tube. The honeysuckles, mints, huckleberry, lilac, etc., are familiar representatives of the _Sympetalæ_, which includes the highest of all plants.

The _Choripetalæ_ may be divided into six groups, including twenty-two orders. The first group is called _Iulifloræ_, and contains numerous, familiar plants, mostly trees. In these plants, the flowers are small and inconspicuous, and usually crowded into dense catkins, as in willows (Fig. 96) and poplars, or in spikes or heads, as in the lizard-tail (Fig. 97, _G_), or hop (Fig. 97, _I_). The individual flowers are very small and simple in structure, being often reduced to the gynœcium or andræcium, carpels and stamens being almost always in separate flowers. The outer leaves of the flower (sepals and petals) are either entirely wanting or much reduced, and never differentiated into calyx and corolla.

In the willows (Fig. 96) the stamens are bright-colored, so that the flowers are quite showy, and attract numerous insects which visit them for pollen and nectar, and serve to carry the pollen to the pistillate flowers, thus insuring their fertilization. In the majority of the group, however, the flowers are wind-fertilized. An excellent example of this is seen in the common hazel (Fig. 97, _A_). The male flowers are produced in great numbers in drooping catkins at the ends of the branches, shedding the pollen in early spring before the leaves unfold. The female flowers are produced on the same branches, but lower down, and in much smaller numbers. The stigmas are long, and covered with minute hairs that catch the pollen which is shaken out in clouds every time the plant is shaken by the wind, and falls in a shower over the stigmas. A similar arrangement is seen in the oaks, hickories, and walnuts.

There are three orders of the _Iulifloræ_: _Amentaceæ_, _Piperineæ_, and _Urticinæ_. The first contains the birches (_Betulaceæ_); oaks, beeches, hazels, etc. (_Cupuliferæ_); walnuts and hickories (_Juglandeæ_); willows and poplars (_Salicaceæ_). They are all trees or shrubs; the fruit is often a nut, and the embryo is very large, completely filling it.

The _Piperineæ_ are mostly tropical plants, and include the pepper plant (_Piper_), as well as other plants with similar properties. Of our native forms, the only common one is the lizard-tail (_Saururus_), not uncommon in swampy ground. In these plants, the calyx and corolla are entirely absent, but the flowers have both carpels and stamens (Fig. 97, _H_).

The _Urticinæ_ include, among our common plants, the nettle family (_Urticaceæ_); plane family (_Plataneæ_), represented by the sycamore or buttonwood (_Platanus_); the hemp family (_Cannabineæ_); and the elm family (_Ulmaceæ_). The flowers usually have a calyx, and may have only stamens or carpels, or both. Sometimes the part of the stem bearing the flowers may become enlarged and juicy, forming a fruit-like structure. Well-known examples of this are the fig and mulberry.

The second group of the _Choripetalæ_ is called _Centrospermæ_, and includes but a single order comprising seven families, all of which, except one (_Nyctagineæ_), are represented by numerous native species. The latter comprises mostly tropical plants, and is represented in our gardens by the showy "four-o'clock" (_Mirabilis_). In this plant, as in most of the order, the corolla is absent, but here the calyx is large and brightly colored, resembling closely the corolla of a morning-glory or petunia. The stamens are usually more numerous than the sepals, and the pistil, though composed of several carpels, has, as a rule, but a single cavity with the ovules arising from the base, though sometimes the ovary is several celled.

The first family (_Polygoneæ_) is represented by the various species of _Polygonum_ (knotgrass, smart-weed, etc.), and among cultivated plants by the buckwheat (_Fagopyrum_). The goose-foot or pig-weed (_Chenopodium_) among native plants, and the beet and spinach of the gardens are examples of the family _Chenopodiaceæ_. Nearly resembling the last is the amaranth family (_Amarantaceæ_), of which the showy amaranths and coxcombs of the gardens, and the coarse, green amaranth or pig-weed are representatives.

The poke-weed (_Phytolacca_) (Fig. 98, _K_), so conspicuous in autumn on account of its dark-purple clusters of berries and crimson stalks, is our only representative of the family _Phytolaccaceæ_. The two highest families are the purslane family (_Portulacaceæ_) and pink family (_Caryophylleæ_). These are mostly plants with showy flowers in which the petals are large and conspicuous, though some of the pink family, _e.g._ some chick-weeds, have no petals. Of the purslane family the portulacas of the gardens, and the common purslane or "pusley," and the spring-beauty (_Claytonia_) (Fig. 98, _A_) are the commonest examples. The pink family is represented by many common and often showy plants. The carnation, Japanese pinks, and sweet-william, all belonging to the genus _Dianthus_, of which there are also two or three native species, are among the showiest of the family. The genera _Lychnis_ and _Silene_ (Fig. 98, _L_) also contain very showy species. Of the less conspicuous genera, the chick-weeds (_Cerastium_ and _Stellaria_) are the most familiar.

The third group of the _Choripetalæ_ (the _Aphanocyclæ_) is a very large one and includes many common plants distributed among five orders. The lower ones have all the parts of the flower entirely separate, and often indefinite in number; the higher have the gynœcium composed of two or more carpels united to form a compound pistil.

The first order (_Polycarpæ_) includes ten families, of which the buttercup family (_Ranunculaceæ_) is the most familiar. The plants of this family show much variation in the details of the flowers, which are usually showy, but the general plan is much the same. In some of them, like the anemones (Fig. 99, _A_), clematis, and others, the corolla is absent, but the sepals are large and brightly colored so as to appear like petals. In the columbine (_Aquilegia_) (Fig. 99, _F_) the petals are tubular, forming nectaries, and in the larkspur (Fig. 99, _T_) one of the sepals is similarly changed.

Representing the custard-apple family (_Anonaceæ_) is the curious papaw (_Asimina_), common in many parts of the United States (Fig. 100, _A_). The family is mainly a tropical one, but this species extends as far north as southern Michigan.

The magnolia family (_Magnoliaceæ_) has several common members, the most widely distributed being, perhaps, the tulip-tree (_Liriodendron_) (Fig. 100, _C_), much valued for its timber. Besides this there are several species of magnolia, the most northerly species being the sweet-bay (_Magnolia glauca_) of the Atlantic States, and the cucumber-tree (_M. acuminata_); the great magnolia (_M. grandiflora_) is not hardy in the northern states.

The sweet-scented shrub (_Calycanthus_) (Fig. 100, _G_) is the only member of the family _Calycanthaceæ_ found within our limits. It grows wild in the southern states, and is cultivated for its sweet-scented, dull, reddish flowers.

The barberry (_Berberis_) (Fig. 101, _A_) is the type of the family _Berberideæ_, which also includes the curious mandrake or may-apple (_Podophyllum_) (Fig. 101, _D_), and the twin-leaf or rheumatism-root (_Jeffersonia_), whose curious seed vessel is shown in Figure 101, _G_. The fruit of the barberry and may-apple are edible, but the root of the latter is poisonous.

The curious woody twiner, moon-seed (_Menispermum_) (Fig. 101, _I_), is the sole example in the northern states of the family _Menispermeæ_ to which it belongs. The flowers are diœcious, and the pistillate flowers are succeeded by black fruits looking like grapes. The flattened, bony seed is curiously sculptured, and has the embryo curled up within it.

The last two families of the order, the laurel family (_Laurineæ_) and the nutmeg family (_Myristicineæ_) are mostly tropical plants, characterized by the fragrance of the bark, leaves, and fruit. The former is represented by the sassafras and spice-bush, common throughout the eastern United States. The latter has no members within our borders, but is familiar to all through the common nutmeg, which is the seed of _Myristica fragrans_ of the East Indies. "Mace" is the "aril" or covering of the seed of the same plant.

The second order of the _Aphanocyclæ_ comprises a number of aquatic plants, mostly of large size, and is known as the _Hydropeltidinæ_. The flowers and leaves are usually very large, the latter usually nearly round in outline, and frequently with the stalk inserted near the middle. The leaves of the perigone are numerous, and sometimes merge gradually into the stamens, as we find in the common white water-lily (_Castalia_).

There are three families, all represented within the United States. The first (_Nelumbieæ_) has but a single species, the yellow lotus or nelumbo (_Nelumbo lutea_), common in the waters of the west and southwest, but rare eastward (Fig. 101, _F_). In this flower, the end of the flower axis is much enlarged, looking like the rose of a watering-pot, and has the large, separate carpels embedded in its upper surface. When ripe, each forms a nut-like fruit which is edible. There are but two species of _Nelumbo_ known, the second one (_N. speciosa_) being a native of southeastern Asia, and probably found in ancient times in Egypt, as it is represented frequently in the pictures and carvings of the ancient Egyptians. It differs mainly from our species in the color of its flowers which are red instead of yellow. It has recently been introduced into New Jersey where it has become well established in several localities.

The second family (_Cabombeæ_) is also represented at the north by but one species, the water shield (_Brasenia_), not uncommon in marshes. Its flowers are quite small, of a dull-purple color, and the leaves oval in outline and centrally peltate, _i.e._ the leaf stalk inserted in the centre. The whole plant is covered with a transparent gelatinous coat.

The third family (_Nymphæaceæ_) includes the common white water-lilies (_Castalia_) and the yellow water-lilies (_Nymphæa_) (Fig. 102, _A_). In the latter the petals are small and inconspicuous (Fig. 102, _C_, _p_), but the sepals are large and showy. In this family the carpels, instead of being separate, are united into a large compound pistil. The water-lilies reach their greatest perfection in the tropics, where they attain an enormous size, the white, blue, or red flowers of some species being thirty centimetres or more in diameter, and the leaves of the great _Victoria regia_ of the Amazon reaching two metres or more in width.

The third order of the _Aphanocyclæ_ (_Rhœadinæ_ or _Crucifloræ_) comprises a number of common plants, principally characterized by having the parts of the flowers in twos or fours, so that they are more or less distinctly cross-shaped, whence the name _Crucifloræ_.

There are four families, of which the first is the poppy family (_Papaveraceæ_), including the poppies, eschscholtzias, Mexican or prickly poppy (_Argemone_), etc., of the gardens, and the blood-root (_Sanguinaria_), celandine poppy (_Stylophorum_), and a few other wild plants (see Fig. 103, _A-I_). Most of the family have a colored juice (latex), which is white in the poppy, yellow in celandine and _Argemone_, and orange-red in the blood-root. From the latex of the opium poppy the opium of commerce is extracted.

The second family, the fumitories (_Fumariaceæ_) are delicate, smooth plants, with curious flowers and compound leaves. The garden bleeding-heart (_Dicentra spectabilis_) and the pretty, wild _Dicentras_ (Fig. 103, _F_) are familiar to nearly every one.

Other examples are the mountain fringe (_Adlumia_), a climbing species, and several species of _Corydalis_, differing mainly from _Dicentra_ in having the corolla one-sided.

The mustard family (_Cruciferæ_) comprises by far the greater part of the order. The shepherd's-purse, already studied, belongs here, and may be taken as a type of the family. There is great uniformity in all as regards the flowers, so that the classification is based mainly on differences in the fruit and seeds. Many of the most valuable garden vegetables, as well as a few more or less valuable wild plants, are members of the family, which, however, includes some troublesome weeds. Cabbages, turnips, radishes, with all their varieties, belong here, as well as numerous species of wild cresses. A few like the wall-flower (_Cheiranthus_) and stock (_Matthiola_) are cultivated for ornament.

The last family is the caper family (_Capparideæ_), represented by only a few not common plants. The type of the order is _Capparis_, whose pickled flower-buds constitute capers.

The fourth order (_Cistifloræ_) of the _Aphanocyclæ_ is a very large one, but the majority of the sixteen families included in it are not represented within our limits. The flowers have the sepals and petals in fives, the stamens either the same or more numerous.

Among the commoner members of the order are the mignonettes (_Resedaceæ_) and the violets (_Violaceæ_), of which the various wild and cultivated species are familiar plants (Fig. 104, _A_, _M_). The sundews (_Droseraceæ_) are most extraordinary plants, growing in boggy land over pretty much the whole world. They are represented in the United States by several species of sundew (_Drosera_), and the still more curious Venus's-flytrap (_Dionæa_) of North Carolina. The leaves of the latter are sensitive, and composed of two parts which snap together like a steel trap. If an insect lights upon the leaf, and touches certain hairs upon its upper surface, the two parts snap together, holding the insect tightly. A digestive fluid is secreted by glands upon the inner surface of the leaf, and in a short time the captured insect is actually digested and absorbed by the leaves. The same process takes place in the sundew (Fig. 104, _N_) where, however, the mechanism is somewhat different. Here the tentacles, with which the leaf is studded, secrete a sticky fluid which holds any small insect that may light upon it. The tentacles now slowly bend inward and finally the edges of the leaf as well, until the captured insect is firmly held, when a digestive process, similar to that in _Dionœa_, takes place. This curious habit is probably to be explained from the position where the plant grows, the roots being in water where there does not seem to be a sufficient supply of nitrogenous matter for the wants of the plant, which supplements the supply from the bodies of the captured insects.

Similar in their habits, but differing much in appearance from the sundews, are the pitcher-plants (_Sarraceniaceæ_), of which one species (_Sarracenia purpurea_) is very common in peat bogs throughout the northern United States. In this species (Fig. 105, _A_, _B_), the leaves form a rosette, from the centre of which arises in early summer a tall stalk bearing a single, large, nodding, dark-reddish flower with a curious umbrella-shaped pistil. The leaf stalk is hollow and swollen, with a broad wing on one side, and the blade of the leaf forms a sort of hood at the top. The interior of the pitcher is covered above with stiff, downward-pointing hairs, while below it is very smooth. Insects readily enter the pitcher, but on attempting to get out, the smooth, slippery wall at the bottom, and the stiff, downward-directed hairs above, prevent their escape, and they fall into the fluid which fills the bottom of the cup and are drowned, the leaf absorbing the nitrogenous compounds given off during the process of decomposition. There are other species common in the southern states, and a California pitcher-plant (_Darlingtonia_) has a colored appendage at the mouth of the pitcher which serves to lure insects into the trap.

Another family of pitcher-plants (_Nepentheæ_) is found in the warmer parts of the old world, and some of them are occasionally cultivated in greenhouses. In these the pitchers are borne at the tips of the leaves attached to a long tendril.

Two other families of the order contain familiar native plants, the rock-rose family (_Cistaceæ_), and the St. John's-worts (_Hypericaceæ_). The latter particularly are common plants, with numerous showy yellow flowers, the petals usually marked with black specks, and the leaves having clear dots scattered through them. The stamens are numerous, and often in several distinct groups (Fig. 105, _C_, _D_).

The last order of the _Aphanocyclæ_ (the _Columniferæ_) has three families, of which two, the mallows (_Malvaceæ_), and the lindens (_Tiliaceæ_), include well-known species. Of the former, the various species of mallows (Fig. 106, _A_) belonging to the genus _Malva_ are common, as well as some species of _Hibiscus_, including the showy swamp _Hibiscus_ or rose-mallow (_H. moscheutos_), common in salt marshes and in the fresh-water marshes of the great lake region. The hollyhock and shrubby _Althæa_ are familiar cultivated plants of this order, and the cotton-plant (_Gossypium_) also belongs here. In all of these the stamens are much branched, and united into a tube enclosing the style. Most of them are characterized also by the development of great quantities of a mucilaginous matter within their tissues.

The common basswood (_Tilia_) is the commonest representative of the family _Tiliaceæ_ (Fig. 106, _G_). The nearly related European linden, or lime-tree, is sometimes planted. Its leaves are ordinarily somewhat smaller than our native species, which it, however, closely resembles.

The fourth group of the _Choripetalæ_ is the _Eucyclæ_. The flowers most commonly have the parts in fives, and the stamens are never more than twice as many as the sepals. The carpels are usually more or less completely united into a compound pistil. There are four orders, comprising twenty-five families.

The first order (_Gruinales_) includes six families, consisting for the most part of plants with conspicuous flowers. Here belong the geraniums (Fig. 107, _A_), represented by the wild geraniums and crane's-bill, and the very showy geraniums (_Pelargonium_) of the gardens. The nasturtiums (_Tropæolum_) represent another family, mostly tropical, and the wood-sorrels (_Oxalis_) (Fig. 107, _I_) are common, both wild and cultivated. The most useful member of the order is unquestionably the common flax (_Linum_), of which there are also several native species (Fig. 107, _F_). These are types of the flax family (_Linaceæ_). Linen is the product of the tough, fibrous inner bark of _L. usitatissimum_, which has been cultivated for its fibre from time immemorial. The last family is the balsam family (_Balsamineæ_). The jewel-weed or touch-me-not (_Impatiens_), so called from the sensitive pods which spring open on being touched, is very common in moist ground everywhere (Fig. 107, _L-P_). The garden balsam, or lady's slipper, is a related species (_I. balsamina_).

The second order (_Terebinthinæ_) contains but few common plants. There are six families, mostly inhabitants of the warmer parts of the world. The best-known members of the order are the orange, lemon, citron, and their allies. Of our native plants the prickly ash (_Zanthoxylum_), and the various species of sumach (_Rhus_), are the best known. In the latter genus belong the poison ivy (_R. toxicodendron_) and the poison dogwood (_R. venenata_). The Venetian sumach or smoke-tree (_R. Cotinus_) is commonly planted for ornament.

The third order of the _Eucyclæ_, the _Æsculinæ_, embraces six families, of which three, the horsechestnuts, etc. (_Sapindaceæ_), the maples (_Aceraceæ_), and the milkworts (_Polygalaceæ_), have several representatives in the northern United States. Of the first the buckeye (_Æsculus_) (Fig. 108, _J_) and the bladder-nut (_Staphylea_) (Fig. 108, _G_) are the commonest native genera, while the horsechestnut (_Æsculus hippocastanum_) is everywhere planted.

The various species of maple (_Acer_) are familiar examples of the _Aceraceæ_ (see Fig. 106, _A_, _F_).

The fourth and last order of the _Eucyclæ_, the _Frangulinæ_, is composed mainly of plants with inconspicuous flowers, the stamens as many as the petals. Not infrequently they are diœcious, or in some, like the grape, some of the flowers may be unisexual while others are hermaphrodite (_i.e._ have both stamens and pistil). Among the commoner plants of the order may be mentioned the spindle-tree, or burning-bush, as it is sometimes called (_Euonymus_) (Fig. 109, _A_), and the climbing bitter-sweet (_Celastrus_) (Fig. 109, _D_), belonging to the family _Celastraceæ_; the holly and black alder, species of _Ilex_, are examples of the family _Aquifoliaceæ_; the various species of grape (_Vitis_), the Virginia creeper (_Ampelopsis quinquefolia_), and one or two other cultivated species of the latter, represent the vine family (_Vitaceæ_ or _Ampelidæ_), and the buckthorn (_Rhamnus_) is the type of the _Rhamnaceæ_.

The fifth group of the _Choripetalæ_ is a small one, comprising but a single order (_Tricoccæ_). The flowers are small and inconspicuous, though sometimes, as in some _Euphorbias_ and the showy _Poinsettia_ of the greenhouses, the leaves or bracts surrounding the inflorescence are conspicuously colored, giving the whole the appearance of a large, showy, single flower. In northern countries the plants are mostly small weeds, of which the various spurges or _Euphorbias_ are the most familiar. These plants (Fig. 109, _K_) have the small flowers surrounded by a cup-shaped involucre (_L_, _M_) so that the whole inflorescence looks like a single flower. In the spurges, as in the other members of the order, the flowers are very simple, being often reduced to a single stamen or pistil (Fig. 109, _M_, _N_). The plants generally abound in a milky juice which is often poisonous. This juice in a number of tropical genera is the source of India-rubber. Some genera like the castor-bean (_Ricinus_) and _Croton_ are cultivated for their large, showy leaves.

The water starworts (_Callitriche_), not uncommon in stagnant water, represent the family _Callitrichaceæ_, and the box (_Buxus_) is the type of the _Buxaceæ_.

The last and highest group of the _Choripetalæ_, the _Calycifloræ_, embraces a very large assemblage of familiar plants, divided into eight orders and thirty-two families. With few exceptions, the floral axis grows up around the ovary, carrying the outer floral leaves above it, and the ovary appears at the bottom of a cup around whose edge the other parts of the flower are arranged. Sometimes, as in the fuchsia, the ovary is grown to the base of the cup or tube, and thus looks as if it were outside the flower. Such an ovary is said to be "inferior" in distinction from one that is entirely free from the tube, and thus is evidently within the flower. The latter is the so-called "superior" ovary. The carpels are usually united into a compound pistil, but may be separate, as in the stonecrop (Fig. 111, _E_), or strawberry (Fig. 114, _C_).

The first order of the _Calycifloræ_ (_Umbellifloræ_) has the flowers small, and usually arranged in umbels, _i.e._ several stalked flowers growing from a common point. The ovary is inferior, and there is a nectar-secreting disc between the styles and the stamens. Of the three families, the umbel-worts or _Umbelliferæ_ is the commonest. The flowers are much alike in all (Fig. 110, _A_, _B_), and nearly all have large, compound leaves with broad, sheathing bases. The stems are generally hollow. So great is the uniformity of the flowers and plant, that the fruit (Fig. 110, _D_) is generally necessary before the plant can be certainly recognized. This is two-seeded in all, but differs very much in shape and in the development of oil channels, which secrete the peculiar oil that gives the characteristic taste to the fruits of such forms as caraway, coriander, etc. Some of them, like the wild parsnip, poison hemlock, etc., are violent poisons, while others like the carrot are perfectly wholesome.

The wild spikenard (_Aralia_) (Fig. 110, _F_), ginseng, and the true ivy (_Hedera_) are examples of the _Araliaceæ_, and the various species of dogwood (_Cornus_) (Fig. 110, _J-N_) represent the dogwood family (_Corneæ_).

The second order (_Saxifraginæ_) contains eight families, including a number of common wild and cultivated plants. The true saxifrages are represented by several wild and cultivated species of _Saxifraga_, the little bishop's cap or mitre-wort (_Mitella_) (Fig. 111, _D_), and others. The wild hydrangea (Fig. 111, _F_) and the showy garden species represent the family _Hydrangeæ_. In these some of the flowers are large and showy, but with neither stamens nor pistils (neutral), while the small, inconspicuous flowers of the central part of the inflorescence are perfect. In the garden varieties, all of the flowers are changed, by selection, into the showy, neutral ones. The syringa or mock orange (_Philadelphus_) (Fig. 111, _I_), the gooseberry, and currants (_Ribes_) (Fig. 111, _A_), and the stonecrop (_Sedum_) (Fig. 111, _E_) are types of the families _Philadelpheæ_, _Ribesieæ_, and _Crassulaceæ_.

The third order (_Opuntieæ_) has but a single family, the cacti (_Cactaceæ_). These are strictly American in their distribution, and inhabit especially the dry plains of the southwest, where they reach an extraordinary development. They are nearly or quite leafless, and the fleshy, cylindrical, or flattened stems are usually beset with stout spines. The flowers (Fig. 112, _A_) are often very showy, so that many species are cultivated for ornament and are familiar to every one. The beautiful night-blooming cereus, of which there are several species, is one of these. A few species of prickly-pear (_Opuntia_) occur as far north as New York, but most are confined to the hot, dry plains of the south and southwest.

The fourth order (_Passiflorinæ_) are almost without exception tropical plants, only a very few extending into the southern United States. The type of the order is the passion-flower (_Passiflora_) (Fig. 112, _B_), whose numerous species are mostly inhabitants of tropical America, but a few reach into the United States. The only other members of the order likely to be met with by the student are the begonias, of which a great many are commonly cultivated as house plants on account of their fine foliage and flowers. The leaves are always one-sided, and the flowers monœcious.[13] Whether the begonias properly belong with the _Passiflorinæ_ has been questioned.

[13] Monœcious: having stamens and carpels in different flowers, but on the same plant.

The fifth order (_Myrtifloræ_) have regular four-parted flowers with usually eight stamens, but sometimes, through branching of the stamens, these appear very numerous. The myrtle family, the members of which are all tropical or sub-tropical, gives name to the order. The true myrtle (_Myrtus_) is sometimes cultivated for its pretty glossy green leaves and white flowers, as is also the pomegranate whose brilliant, scarlet flowers are extremely ornamental. Cloves are the dried flower-buds of an East-Indian myrtaceous tree (_Caryophyllus_). In Australia the order includes the giant gum-trees (_Eucalyptus_), the largest of all known trees, exceeding in size even the giant trees of California.

Among the commoner _Myrtifloræ_, the majority belong to the two families _Onagraceæ_ and _Lythraceæ_. The former includes the evening primroses (_Œnothera_), willow-herb (_Epilobium_) (Fig. 113, _D_), and fuchsia; the latter, the purple loosestrife (_Lythrum_) and swamp loosestrife (_Nesæa_). The water-milfoil (_Myriophyllum_) (Fig. 113, _J_) is an example of the family _Haloragidaceæ_, and the _Rhexias_ of the eastern United States represent with us the family _Melastomaceæ_.

The sixth order of the _Calycifloræ_ is a small one (_Thymelinæ_), represented in the United States by very few species. The flowers are four-parted, the calyx resembling a corolla, which is usually absent. The commonest member of the order is the moosewood (_Dirca_) (Fig. 113, _A_), belonging to the first of the three families (_Thymelæaceæ_). Of the second family (_Elæagnaceæ_), the commonest example is _Shepherdia_, a low shrub having the leaves covered with curious, scurfy hairs that give them a silvery appearance. The third family (_Proteaceæ_) has no familiar representatives.

The seventh order (_Rosifloræ_) includes many well-known plants, all of which may be united in one family (_Rosaceæ_), with several sub-families. The flowers are usually five-parted with from five to thirty stamens, and usually numerous, distinct carpels. In the apple and pear (Fig. 114, _I_), however, the carpels are more or less grown together; and in the cherry, peach, etc., there is but a single carpel giving rise to a single-seeded stone-fruit (drupe) (Fig. 114, _E_, _H_). In the strawberry (Fig. 114, _A_), rose (_G_), cinquefoil (_Potentilla_), etc., there are numerous distinct, one-seeded carpels, and in _Spiræa_ (Fig. 114, _F_) there are five several-seeded carpels, forming as many dry pods when ripe. The so-called "berry" of the strawberry is really the much enlarged flower axis, or "receptacle," in which the little one-seeded fruits are embedded, the latter being what are ordinarily called the seeds.

From the examples given, it will be seen that the order includes not only some of the most ornamental, cultivated plants, but the majority of our best fruits. In addition to those already given, may be mentioned the raspberry, blackberry, quince, plum, and apricot.

The last order of the _Calycifloræ_ and the highest of the _Choripetalæ_ is the order _Leguminosæ_, of which the bean, pea, clover, and many other common plants are examples. In most of our common forms the flowers are peculiar in shape, one of the petals being larger than the others, and covering them in the bud. This petal is known as the standard. The two lateral petals are known as the wings, and the two lower and inner are generally grown together forming what is called the "keel" (Fig. 115, _A_, _B_). The stamens, ten in number, are sometimes all grown together into a tube, but generally the upper one is free from the others (Fig. 115, _C_). There is but one carpel which forms a pod with two valves when ripe (Fig. 115, _D_). The seeds are large, and the embryo fills the seed completely. From the peculiar form of the flower, they are known as _Papilionaceæ_ (_papilio_, a butterfly). Many of the _Papilionaceæ_ are climbers, either having twining stems, as in the common beans, or else with part of the leaf changed into a tendril as in the pea (Fig. 115, _A_), vetch, etc. The leaves are usually compound.

Of the second family (_Cæsalpineæ_), mainly tropical, the honey locust (_Gleditschia_) and red-bud (_Cercis_) (Fig. 115, _G_) are the commonest examples. The flowers differ mainly from the _Papilionaceæ_ in being less perfectly papilionaceous, and the stamens are almost entirely distinct (Fig. 115, _H_). The last family (_Mimosaceæ_) is also mainly tropical. The acacias, sensitive-plant (_Mimosa_), and the sensitive-brier of the southern United States (_Schrankia_) (Fig. 115, _I_) represent this family. The flowers are quite different from the others of the order, being tubular and the petals united, thus resembling the flowers of the _Sympetalæ_. The leaves of _Mimosa_ and _Schrankia_ are extraordinarily sensitive, folding up if irritated.