Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/144

Rh 128 VEGETABLE KINGDOM agineas is made in accordance with the views of recent writers, such as De Baiy and Brefeld, the Ustilagincse being regarded as sexually degenerate Zygomycetcs. A brief description of the newly introduced orders, namely, the Chytridicwese, the ISntomophthoreee, the Ancylistese, and the Gymno- asceie, may be given. The Chytridiacete are extremely simple Fungi, consisting in some forms of a single spherical cell and in others of a small mycelium. The Entomophthoreie have a well- developed mycelium, which, unlike that of most Phy corny cetes, is septate. The Ancylisteae, are merely the simplest forms of the Oomycetes. The Gymnoascess, are characterized by the simple struc ture of their fructification, the asci (or, in some cases, the single ascus) not being surrounded by an investment of sterile tissue. This group includes typical forms, such as Gymnoascus and Ercm- ascus, as well as aberrant forms, such as Exoascus, Saccharomyces, &c. Mutual Affinities and Phytogeny of Sub-Classes of Fungi. The Myxomycetes and the Schizomycetes are so peculiar that they cannot be connected in any way with the other sub-classes of Fungi. Beginning, then, with the Zygomycctcs, there can be no doubt that the Chytridiaceee, are closely connected with the Mucorini by such forms as Polyphagus and Zygochytrium, and with the Ancylistese among the Oomycetes. On the other hand, they are connected with the Ustilaginc.se, (especially Protomyces) by Clado- chytrium. The Entomophthoress seem to be most nearly related to the Mucorini. The Ancylistese are closely related to the Perono- sporese (especially Pythium), and these again to the Saprolegniese. Coming now to the Ascomycetes, there is an obvious similarity be tween the simpler Gymnoascess and the Mucorini. Thus in Eremascus the sexual organs are quite similar, and the sexual process is one of conjugation, as in the Mucorini ; but there is this difference, that the product of the sexual process in Eremascus is an ascus, whereas in the Mucorini it is a zygospore (see REPRODUCTION). Those Ascomycetes which, like Pyronema, have differentiated sexual organs, show some resemblance to the Oomycetes. The Uredinese, appear to be closely connected with the Ascomycetes on the one hand, the secidium being homologous with the apothecium, and on the other hand with the Tremellini among the Basidiomycetes, through the Tremelloid Uredinese, (Leptopucciniese), which have lost their aecidia, possessing only asexually- produced spores (teleutospores). The Jfymenomycetes and the G aster mny cetes appear to form two parallel series starting from the Tremellini. In attempting to express these relations in terms of phylogeny, the first question which arises is as to whether or not the Chytri- diaccee, are to be taken as the primitive forms. It is possible to regard them, not as primitive forms, but as degraded Mucorini, their degradation being due to their aquatic habit ; but there are no conclusive grounds for this assumption. Then there is the ques tion as to the origin of the Ascomycetes. De Bary inclines to the opinion that they are derived from the Oomycetes (especially Perono- spora), on account of the similarity of the sexual organs of such Ascomycetes as Podosphsera to those of the Peronosporeaz. But how, on this view, is the development of Ascomycetes with similar sexual organs to be accounted for ? It seems more reasonable to trace the Ascomycetes back through Eremascus to the Mucorini, and to as sume that the differentiation of the sexual organs arose in the Ascomycetous series. The following scheme expresses the phylogeny of the Fungi as suggested in the foregoing remarks. Chytridiacece (Zygochytrium) I EntomophtJwreK. Mucorini I (Protomyces) Ustilagineee. (Ancylisteas) Oomycetes. (Eremascus) Ascomycetes JEcidiomycetes (Tremelloid Uredinece) Basidiomycetes Tremellini I I I Hymenomycetes. Gasteromycetes. Affinities of Fungi with Algse. With the exception of the Basidiomycetes, the sub-classes of Fungi present resemblances to various forms of Algae, as might be expected, for the Fungi must have sprung from the Algss. The Myxomycetes resemble the Hydrodictyeee, in that the body (plas- modiurn) is a coenobium, formed by the aggregation of originally separate cells. The similarity of the Schizomyceies to the Cyano- phyceas has been already mentioned (p. 125). The Phycomycetes resemble the Siphoncse in their typically unseptate multinucleate structure ; but the Mucorini approach the Conjugate Algse, and the Oomycetes the oogamous Siphonese, in the sexual process. The simpler Chytridiocese closely resemble the Protococcaceae in their general form, as also in the production of ciliated zoospores. The Ascomycetes, especially those in which male cells (spermatia) are formed, and probably also the ^Ecidiomycetes, resemble the Rhodo- pliycese, in many important features. In both groups the female organ contains no distinctly differentiated female cell (oosphere) ; and the effect of fertilization is to cause the female organ to grow into a sporogenous fructification (apothecium, cystocarp), which con stitutes the asexual generation or sporophyte in the life -history. AVith regard to the derivation of the Fungi from the Algae, it appears that there are at least two distinct origins. The Schizomy- cetes doubtless arose from the Cyanopliyccaz ; but, as pointed out above, the Schizomycetes cannot be regarded as having given rise to higher forms of Fungi. These sprang independently from the Algte ; and probably the Chytridiacefe, were derived from the Proto- coccaccas ; and from the Cliytridiaccee, the higher forms were developed as indicated in the above sketch of the phylogeny of the Fungi, the evolution of the Fungi proceeding along much the same lines as that of the Algse, and thus giving rise to forms which have their representatives in the Algae, and terminating in the Basidiomycetes, which are altogether and peculiarly Fungal. The origin of the Chytridiacese from the Protococcaceae, is suggested by the fact that many of the latter are &quot;endophytic&quot; : that is, they inhabit the tissues of higher plants ; and the Chytridiacese may be regarded as Protococcaccse which have become truly parasitic, and have conse quently lost their chlorophyll. Additional Literature to t lingi. De Bary and Woronin, Beitrage ziir Mor- phologie und Physiologie der Pilze, 4th and 5th series, 1881-82 ; Brefeld, Un- tersuchungen, parts v.-vii., 1883-88; De Bary, Comparative Morphology and Biology of the Fungi, Oxford, 1887. SUBSIDIARY GKOUP, LICHENES. As pointed out in the article FUNGUS, a Lichen is a compound organism consist ing of a Fungus and an Alga living symbiotically. In that article only those Lichens are considered in which the Fungus belongs to the Ascomycetes ; but Lichens are now known in which the Fungus belongs to the Basidiomycetes. The Lichens may be classified as follows : Ascolichenes (Ascomycetous Lichens). 1. Discolichenes (Discomycetous Lichens). 2. Pyrenolichcncs (Pyrenomycetous Lichens). Basidiolichencs (Basidiomycetous Lichens). 1. Hymcnoliehenes(}lymenomycetous Lichens). 2. G aster olichenes (Gasteroinycetous Lichens). Literature. Massee, &quot;OnGasterolichenes,&quot;in.P/Uz. Trans., vol. clxxviii., 188&quot;. SUB-KINGDOM II. BRYOPHYTA (Muscines&). The Bryopliyta may be characterized as plants which pre sent a definite alternation of generations, the plant being the gametophyte and the fructification or sporogonium the sporophyte. The sporophyte is not independent, but remains permanently attached to the gametophyte. The shoot of the gametophyte is sometimes thalloid ; but more frequently it is differentiated into stem and leaf. The shoot of the sporophyte is not differentiated into stem and leaf, though there is in some cases an indication of such differentiation. The gametophyte commonly reproduces its like by means of gemmae ; the female organ is an arche- gonium. The Bryophyta are divided into two classes the HEPATIOE or LIVERWORTS and the Musci or MOSSES. (For details see MUSCINE.E.) Mutual Affinities and Phylogeny of Mosses and Liverworts. In consequence of the well-marked alternation of generations in these classes, it is essential to trace their resemblances in both generations. a. Gametophyte (plant). The higher Liverworts (foliose Junger- manniese) resemble the Mosses in that the shoot is differentiated into stem and leaf ; but there is this general difference, that the shoot of these Liverworts has dorsi-ventral symmetry, whereas that of the Mosses has radial symmetry. The connecting form is afforded by Naplomitrium, which alone among the foliose Liverworts has radial symmetry. b. Sporophyte (sporogonium). The main differences between the sporogonium of the Liverworts and that of the Mosses are these : the structure of the sporogonium is simpler in the Liverworts than it is in the Mosses ; in the former it usually has no columella and produces elaters, whereas in the latter a columella is always present, and there are no elaters. In the Liverworts the sporogonium re mains enclosed in the enlarged venter of the archegoninm (calyptra) until the spores are ripe, but in most Mosses the developing sporo gonium bursts the calyptra at an early stage. A connecting form is afforded by the sporogonium of Anthoceros (Liverwort), which has a columella and bears stomata like the sporogonia of the Mosses,