IO2 FIRST GROUP. THALLOPHYTES. 



ment in respect to the mode of formation of the fructification between the Florideae 

 and that section of the Ascomycetes, which by a peculiar association with certain 

 Algae form the organisms known as Lichens. (See below, and for the Basidiomy- 

 cetous lichens, p. 114). In these, as in the Florideae, we find male organs of fertilisa- 

 tion, the spermatia, produced in special receptacles, spermogom'a. The archicarp 

 (ascogone) moreover developes, as in the Florideae, a special receptive apparatus, 

 the trichogyne, with the apex of which the spermatia conjugate, as in the Florideae. 

 In this case therefore there is no antheridial "branch ; the spermatia perform its 

 functions. 



In contrast to this case of sexual production of the fructification in the Ascomy- 

 cetes, many others have recently become known to us, in which there is no trace 

 of sexual organs, archicarp or antheridial branch, preceding the formation of 

 fructification, and therefore no distinction between sterile and fertile hyphae in the 

 fructification. So it is in Pleospora herbarum^, Chaetomium 2 , Pezim Fuckeliana, 

 tuber osa and sclerotiorum 3 ; the sclerotia of the last-named, for example, are formed by 

 the active growth of shoots from branches of the hyphae simultaneously over broad 

 patches of mycelium, and the cup-shaped fructifications arise from inside the sclerotia. 

 during their further development in the form of dense tufts of hyphae. The parts 

 that bear and produce the asci are in this case hyphae, which differ from the adjacent 

 sterile hyphae only in having asci formed as branches on them. In these Ascomy- 

 cetes then the retrogression has gone so far that the sexual organs, the archicarp and 

 the antheridial branch, are no longer formed ; just as we saw in the Saprolegnieae 

 that the formation of antheridial branches had entirely ceased in individuals of 

 several species, and yet the oospores continued to be formed as in all the rest. We 

 shall make acquaintance presently with a similar case of loss of conjugating power, 

 apogamy^ among the Ferns. 



Fig. 62 gives a clear idea of the formation of the spores in the ascus 4 . In 

 the young ascus (Fig. 62, m, r) there is a nucleus which divides in two; the two 

 parts separate (Fig. 62, s\ and each divides again; each of the four parts divides 

 once more, and thus there are now eight free nuclei in the ascus. Cell-formation 

 about them now takes place (Fig. 62, r), each becoming surrounded with protoplasm 

 which forms a membrane on its outer surface. There is little protoplasm in the ripe 

 ascus besides that which forms the spores ; almost all has been used in forming the 

 spores. 



With respect to the structure of the fructification, it is to be remarked that there 

 are some species in which we can scarcely say that there is any fructification. This 

 is the case in Gymnoascus, where the asci spring from branches of the mycelium which 

 are not united into a fructification distinctly delimited, and surrounded by a coherent 

 envelope ; and there is even less appearance of a fructification in Exoascus and the 

 Yeast-fungi, which, as reduced Ascomycetes, will be considered at the close of this 



1 Bauke, Zur Entwicklungsgeschichte d. Ascomyceten (Bot. Ztg. 1877, p. 313). 



2 Zopf, Unters. ii. Chaetomium (Bot. Ztg. 1879, p. 73). 



3 Brefeld, Bot. Unters. u. d. Schimmelpilze, IV. 



* De Bary, Ueber d. Fruchtentwicklung d. Ascomyceten, p. 34. Strasburger, Ueber Zellbildung 

 u. Zelltheilung, III. Aufl. p. 49 ff. Schmitz, Sitzungsber. d. niederrh. Ges. Aug. 1879. P- 2O of the 

 reprint. Compare also the formation of spores in Exoascus and Tuber. 



