Part 16

_Phallus impudicus_ (Stink-horn) (Fig. 179), has a fruit-body which at first is white, heavy, and soft, and resembles a hen’s egg in shape and size. The peridium is divided into three layers (Fig. 179 _e_, _g_, _f_) of which the external and internal are membranous, and the middle one very thick and gelatinous; each of these has again a laminated structure. The peridium when ruptured remains as a sheath (_k_) at the base of the stalk. The receptacle at first is strongly compressed (_h_) but afterwards expands into a long stalk (_l_) which bears the conical gleba (_m_). Prior to the rupture of the peridium the gleba consists of a greenish mass (_i_) which, when exposed, emits a carrion-like stench serving to attract flies, by whose agency the spores are distributed. It is found commonly in hedgerows and in woods, growing on the ground. The much smaller and less common _P. caninus_ is found on rotten tree-stumps.--In _Clathrus cancellatus_ the receptacle expands into a bright red, reticulate structure. A native of the South of Europe. _Colus_, _Aseroë_, _Mitromyces_.

Order 2. =Sphærobolaceæ.= An intermediate layer of the _peridium_ swells when ripe, becomes convex, and _ejects the remaining_ spherical _portion of the fruit-body_ which contains the spores. _Sphærobolus carpobolus_ has small, spherical fruit-bodies which open in the form of a star.

Family 4. =Gasteromycetes.=

The fruit-body is _angiocarpic_, fleshy at first, and later generally more or less _hard_ and _continues closed after the_ spores _are ripe_. The tissue lying immediately inside the _peridium_ is termed the _gleba_; it is porous, containing a larger or smaller number of chambers lined with the hymenium, which is either a continuous layer of basidia or else it fills up the entire cavity. The basidia as a rule bear four spores, sometimes eight (_Geaster_), or two (_Hymenogaster_). The tissue of the walls (_trama_) consists often (_Lycoperdaceæ_) of two kinds of hyphæ, some thin and rich in protoplasm, divided by transverse septa and bearing the basidia; others thicker and thick-walled which do not dissolve like the former on the ripening of the spores, but continue to grow and form a woolly, elastic mass, the _capillitium_, which may be regarded as highly developed paraphyses. The peridium may be either single or double, and presents many variations in its structure and dehiscence. The mycelium is generally a number of string-like strands, living in soils rich in humus.

Order 1. =Tylostomaceæ.= Capillitium present. After the rupture of the peridium the remaining part of the fruit-body is elevated on a long _stalk_. _Tylostoma mammosum_, on heaths.

Order 2. =Lycoperdaceæ.= The fruit-body has a double peridium; the external one at length breaks into fragments (_Lycoperdon_, _Bovista_), or it has a compound structure of several layers (_Geaster_) and detaches itself as a continuous envelope from the inner layer, which is membranous and opens at its apex. The interior of the fruit-body consists either solely of the fertile gleba (_Bovista_, _Geaster_), or, in addition, of a sterile tissue at the base (_Lycoperdon_). A capillitium is also present.

_Lycoperdon_ (Puff-ball) has a sterile part at the base of the fruit-body which often forms a thick stalk. The surface of the peridium is generally covered with warts or projections. When young this Fungus is edible, but when ripe it is dry, and used for stopping the flow of blood. _L. giganteum_, which is often found growing in meadows, attains a considerable size, its diameter reaching as much as eighteen inches. _L. gemmatum_ (Fig. 180) is covered with pyramidal warts; in woods.--_Bovista_ has no sterile basal part; the external peridium is smooth, and falls away in irregular patches. _B. plumbea_, on links near the sea.--_Geaster_ (Earth-star) has an external peridium composed of several layers, which when the fruit-body opens, split into several stellate segments. These segments are very hygroscopic, and in dry weather bend backwards and so raise the inner peridium into the air. The inner peridium contains the spores and capillitia. _G. coliformis_ has several apertures in the inner peridium. The other species have only one regular aperture at the apex. _G. striatus_ has a pedicellate inner peridium, with conical, striped peristome. _G. fornicatus_ has an external peridium split into four segments. This last and several other species produce “mycorhiza” on the roots of Conifers.

Order 3. =Sclerodermataceæ.= _Capillitium_ wanting. The peridium is simple and thick, gleba with round, closed chambers, which are filled with basidia.

_Scleroderma_ has a corky peridium. The fruit-bodies commence their development under ground. _S. vulgare_ (Fig. 181 V-VII), has a hard, slaty-black gleba.

Order 4. =Nidulariaceæ= (=Nest-Fungi=). Small Fungi of which the fruit-body at first is spherical or cylindrical but upon maturity it becomes cupular or vase-like, and contains several lenticular “peridiola” lying like eggs in a nest. The peridiola are the chambers which contain the hymenium, covered by a thin layer of the gleba, all the remaining portion of the gleba becoming dissolved. On decaying wood.

_Nidularia_ has spherical fruit-bodies containing a large number of lenticular peridiola, embedded in a slimy mass.--_Crucibulum_ has fruit-bodies resembling crucibles with discoid peridiola, each with a spirally-twisted stalk.--_Cyathus_ has a fruit-body, which when open is campanulate, with stratified peridium, and long-stalked, lense-shaped peridiola.

Order 5. =Hymenogastraceæ.= Fruit-bodies tubercular, globose and subterranean, resembling very closely the Truffles, from which they can only be distinguished with certainty by microscopic means. The peridium is simple, capillitium wanting, and the gleba encloses a system of labyrinthine passages covered with a continuous hymenium. The fruit-bodies persist for some time, and form a fleshy mass, the spores being only set free by the decay of the fruit-body, or when it is eaten by animals. The majority are South European. _Hymenogaster_, _Melanogaster_, _Rhizopogon_ (Fig. 181 I-IV).

APPENDIX TO THE BASIDIOMYCETES:

Basidiolichenes (Lichen-forming Basidiomycetes).

Several Fungi belonging to the Basidiomycetes have a symbiotic relationship with Algæ exactly similar to that enjoyed by certain Ascomycetes, and these are therefore included under the term Lichens (p. 136). They are chiefly tropical.

Order 1. =Hymenolichenes.= To this order belong some gymnocarpic forms: _Cora_, _Dictyonema_, _Laudatea_.[15]

Order 2. =Gasterolichenes.= To this belong some angiocarpic forms: _Emericella_, _Trichocoma_.

APPENDIX TO THE FUNGI.

Fungi imperfecti (Incompletely known Fungi).

1. The =Saccharomyces-forms= are Fungi which are only known in their yeast-conidial form. They are _conidia of higher Fungi_ which can multiply to an unlimited extent by budding in nutritive solutions, and in this way maintain their _definite_ size and shape. The budding takes place _only at the ends_ of the conidia. The wall of the conidium forms at one or at both ends a small wart-like outgrowth, which gradually becomes larger, and is finally separated from its mother-cell as an independent cell, surrounded by a closed cell-wall (Fig. 182 _a_, _b_).

Under very favourable conditions multiplication occurs so rapidly that the daughter-cells themselves commence to form buds, before they have separated from their mother-cell, with the result that pearl-like chains of cells are produced. When the yeast-cells have only limited nutriment, with an abundant supply of air, at a suitable temperature, an endogenous formation of _spores_ takes place. The protoplasm of the cells divides into 1–4 (rarely a greater number) masses (Fig. 182 _c_, _d_, _e_) which surround themselves with a thick cell-wall, and in this state can withstand adverse conditions and periods of dryness lasting for several months.

The _sporangia are not asci_ since they have no definite form, and a definite number, form and size of spores is not found. The spores in the different species and kinds occupy varying periods for their development, although exposed to the same temperature, a fact of importance in determining one from another. On germination the wall of the mother-cell is destroyed, and each spore gives rise to a new cell, multiplication taking place by budding (Fig. 182 _f_). The majority of Yeast-Fungi are able to produce alcoholic fermentation in saccharine fluids.

The most important of these Fungi is the Beer-yeast (_Saccharomyces cerevisiæ_) with ovate, ellipsoidal or spherical cells (Fig. 182). It is a plant which has been cultivated from time immemorial, on account of its property of producing alcoholic fermentation in sugar-containing extracts (wort), derived from germinating barley (malt). Carbonic acid is also set free during this process. The “surface-yeast” (Fig. 182 _a_), which produces ordinary beer when the brewing takes place at higher temperatures, has cell-chains; “sedimentary yeast” (Fig. 182 _b_), used in the brewing of Bavarian beer, has spherical cells, solitary, or united in pairs. Both these and the following Yeast-Fungi include, according to Hansen, several species and kinds.

The “Ferment of Wine” (_Saccharomyces ellipsoideus_) produces wine in the juice of grapes. Uncultivated yeast-cells are always present on grapes; an addition of this species to the “must” is not necessary to secure fermentation. A large number of other “uncultivated” yeast-cells appear in breweries mixed with the cultivated ones, and cause different tastes to the beer (_S. pastorianus_, etc.). _S. ludwigii_, found, for instance, on the slimy discharge from Oaks, produces abundant cell-chains on cultivation. _S. apiculatus_ is very frequently met with on all kinds of sweet fruits, it has orange-like cells. _S. mycoderma_ has cylindrical cells, often united together in chains (Fig. 183): it forms a whitish-gray mass (“fleur de vin”) on wine, beer, fruit-juice, etc., standing in bottles uncorked or not entirely filled. It is thought that this Fungus causes decomposition and oxydises the fluid in which it is found, but it cannot produce alcoholic fermentation in saccharine liquids, and it does not form endospores; hence it is uncertain whether it is true _Saccharomyces_.

The “Dry-yeast” used in baking white bread is “surface-yeast.” In _leaven_, a kneaded mixture of meal, barm and water, which is used for the manufacture of black bread, _Saccharomyces minor_ is present, and a species allied to this produces alcoholic fermentation in dough with the evolution of carbonic acid, which causes the dough to “rise.”

2. =Oidium-forms.= Of many Fungi only the Oidium-forms are known, which multiply in endless series without employing any higher form of reproduction. _Oidium lactis_ (Fig. 184) is an imperfectly developed form which frequently appears on sour milk and cheese. It can produce a feeble alcoholic fermentation in saccharine liquids. Thrush or aphthæ (_O. albicans_) appears as white spots in the mouths of children. Several similar _Oidium-forms_ are parasites on the skin and hair of human beings, and produce skin diseases, such as scurvy (_O. schoenleinii_) and ringworm (_O. tonsurans_).

3. =Mycorhiza.= These Fungi, which have been found on the roots of many trees and heath-plants, particularly Cupuliferæ and Ericaceæ, consist of septate hyphæ, and belong partly to the Hymenomycetes, partly to the Gasteromycetes. It has been shown that the Mycorhiza enters into a symbiotic relationship with the roots of higher plants.

DIVISION II.

MUSCINEÆ (MOSSES).

In this Division a well-marked alternation of generations is to be found. The development of the first or sexual generation (_gametophyte_),[16] which bears the sexual organs, antheridia and archegonia, commences with the germination of the spore, and consists, in the Liverworts, of a thallus, but in the true Mosses of a filamentous protonema, from which the Moss-plant arises as a lateral bud. The second or asexual generation (_sporophyte_), developed from the fertilised oosphere, consists of a sporangium and stalk.

=The sexual generation, the gametophyte.= The protonema in the Liverworts is very insignificant, and not always very sharply demarcated from the more highly developed parts of the nutritive system. In the true Mosses the protonema is well-developed, and consists of a branched, alga-like filament of cells, the dividing cell-walls being always placed obliquely. In the parts exposed to the light it is green, but colourless or brownish in those parts which are underground (Fig. 186). The protonema is considered to be a lower form of the stem, and grows in the same manner by means of an apical cell; at its apex it may directly develope into a leaf-bearing stem, or these arise from it as lateral branches (Fig. 186 _k_).

The more highly differentiated part of the vegetative system, the “Moss-plant,” which is thus developed from the protonema, is in the “thalloid” Liverworts generally a dichotomously-branched thallus without any trace of leaf-structures (Fig. 194); in _Marchantia_ (Fig. 197) and others, scale-like leaves (_amphigastria_) are found on the under surface. The higher Liverworts and the Leafy-Mosses are differentiated into a filamentous, ramified stem with distinct leaves arranged in a definite manner, resembling the stem and leaves of the higher plants (Figs. 186, 195, 200).

_True roots are wanting_, but are biologically replaced by _rhizoids_. These are developed on the stems or thallus: in the Liverworts they are unicellular, but in the Leafy-Mosses generally multicellular and branched. In the latter group they are considered identical with the protonema, and may become true protonema, and new plants may be developed from them (Fig. 186 _b_).

The internal structure of the sexual generation is very simple. The leaves in nearly all cases are formed of a single-layered plate of cells; in the Leafy-Mosses, however, a midrib is very often formed, and sometimes, also, marginal veins; and along these lines the leaves are several layers of cells in thickness. The stem is constructed of cells longitudinally elongated, the external ones of which are narrower and sometimes have thicker walls than the more central ones. _Vessels are not found_, but in several Mosses there is in the centre of the stem a conducting strand of narrow, longitudinal cells, which represents the vascular bundle in its first stage of development. This strand contains elements for conveying water as well as sieve-tubes. Stomata are entirely wanting in the sexual generation of the Leafy-Mosses; they are found in a few Liverworts (_Marchantia_), but their structure is not the same as in the higher plants.

VEGETATIVE REPRODUCTION takes place by gemmæ or buds which arise on the protenema, the rhizoids, the thallus, or the shoots, and become detached from the mother-plant; or else the protonema and the older parts of the plant simply die off, and their branches thus become independent plants. This well-developed vegetative reproduction explains why so many Mosses grow gregariously. In certain Marchantiaceæ special cupules, in which gemmæ are developed, are found on the surface of the thallus (Fig. 197 _A_, _s-s_). Again, protonema may also arise from the leaves, and thus the leaves may act as reproductive bodies. Certain Mosses nearly always reproduce vegetatively, and in these species the oospheres are seldom fertilised.

The first generation bears the SEXUAL ORGANS; both kinds are found either on the same plant (monœcious), or on separate plants (diœcious). In the thalloid Liverworts they are often situated on the apex of small stems (_gametophores_), springing from the surface of the thallus. In the Leafy-Liverworts and true Mosses the leaves which enclose the sexual organs often assume a peculiar shape, and are arranged more closely than the other leaves to form the so-called “Moss-flower.” The male sexual organs are called _antheridia_. They are stalked, spheroid, club- or egg-shaped bodies whose walls are formed of one layer of cells (Fig. 187), enclosing a mass of minute cubical cells, each one of which is a mother-cell of a spermatozoid. The spermatozoids are self-motile; they are slightly twisted, with two cilia placed anteriorly (Fig. 188), while posteriorly they are generally a trifle club-shaped, and often bear at that part the remains of the cytoplasm, the spermatozoid itself being _formed from the nucleus_. In the presence of water the ripe antheridium bursts, and its contents are ejected; the spermatozoids, being liberated from their mother-cells, swarm about in the water in order to effect fertilisation.

The female sexual organs are termed _archegonia_. They are flask-shaped bodies (Fig. 189), the lower, swollen portion (_venter_) having a wall, in most cases from 1–2 cells thick, enclosing the oosphere (Fig. 189 _B_, _k_): the long neck is formed of tiers of 4–6 cells, enclosing a central row of cells--_the neck-canal-cells_ (Fig. 189 _A_). When the archegonium is fully developed, the walls of the neck-canal-cells become mucilaginous and force open the neck of the archegonium. The mucilage thus escapes, and, remaining at the mouth of the archegonium, acts in a somewhat similar manner to the stigma and conducting tissue of a carpel, by catching and conducting the spermatozoids to the oosphere (Fig. 189 _B_, _m_), with whose cell-nucleus they coalesce. With regard to the formation of the oosphere, it may further be remarked that the lower part of the archegonium originally encloses the so-called “central cell”; but shortly before the archegonium is ripe, this cuts off a small portion, _the ventral-canal-cell_, which lies immediately beneath the neck, and the larger, lower portion becomes the oosphere.

The organs mentioned here, antheridia and archegonia, are present in the Cryptogams (Pteridophyta) and the Gymnosperms. They have always the same fundamental structure, but with slight modifications of detail. These plants are therefore known as the ARCHEGONIATA.

The fertilisation of the Mosses cannot be effected without water. Rain and dew therefore play a very important part in this process, and for this end various modifications of structure are found.

Among the sexual organs, paraphyses--filamentous or club-shaped bodies--are to be found.

=The asexual generation, the sporophyte= (Moss-fruit or sporogonium). As the result of fertilisation the oosphere surrounds itself with a cell-wall, and then commences to divide in accordance with definite laws.[17] The embryo (Fig. 189 _C_) produced by these divisions remains inside the wall _a-a_ of the archegonium (Figs. 190, 199 _D_, _E_), and developes into the _sporogonium_, which remains attached to the mother-plant, often nourished by it, as if the two were one organism. The lower extremity of the sporogonium, _the foot_ (Figs. 190 _f_; 199 _D_), very often forces its way deep down into the tissue of the mother-plant, but without an actual union taking place. The central portion of the sporogonium becomes a shorter or longer _stalk_ (_seta_), while the sporangium itself is developed at the summit. At a later stage, during the formation of the spores, the sporangium very often assumes the form of a _capsule_, and dehisces in several ways characteristic of the various genera (Figs. 192, 193, 194, 195, 200). The basal portion of the archegonium grows for a longer or shorter period, forming a sheath, the _calyptra_, in which the capsule is developed, but eventually it ceases to enlarge, and is then ruptured in different ways, but quite characteristically, in each group. Anatomically, the asexual generation is often more highly differentiated than the sexual; thus, for instance, stomata are present on the sporangia of the true Mosses, but are absent in the sexual generation.