104 FIRST GROUP. THALLOPHYTES. 



and spermatia in spermogonia). It has been shown in several cases that the 

 pycnidia belong to Fungi which are parasitic on the particular Ascomycete ; in 

 others that the pycnidia make their appearance as a further form of gonidial 

 fructification in the Ascomycete. A variety of formations seem to have been 

 included under the term spermogonia ; true spermogonia, receptacles in which 

 male reproductive cells, spermatia, are produced, are known only at present in the 

 Lichen-fungi ; in other Ascomycetes the spermatia are distinguished from the 

 gonidia only by their minuteness and by their being incapable of germination. 



Pycnidia as well as the gonidia produced on free gonidiophores may be wanting, as, 

 for instance, in Tuber ; but in many species, as in the moulds just mentioned, they 

 are produced in enormous quantities, while the sporocarps are seldom formed ; this 

 is the case with Penicillium. 



1. Gymnoascus ', a very small Fungus growing on the dung of horses and sheep, is one 

 of the simplest of Ascomycetes. Its mycelium bears numerous sexual organs, which 

 are exactly alike at the moment of fertilisation. After fertilisation the archicarp divides 

 into a series of cells which develope into short branched filaments with the eight-spored 

 asci in dense masses at their extremities. The investment of the fructification is only 

 rudimentary, and the fertile portion therefore is naked, as in the simplest of the 

 Florideae (Nemaliori). 



2. CLEISTOCARPOUS ASCOMYCETES. 



a. The ERYSIPHEAE 2 form globular fructifications on the surface of the substances 

 which they inhabit. These fructifications are usually so small as scarcely to be seen 

 with the naked eye, while the mycelia attain to a considerable size ; the fructification is 

 enclosed in a thin hollow spherical envelope having a superficial layer of pseudo- 

 parenchyma, and containing one or only a few asci which spring from the archicarp. 



The genus Erysiphe (Mildew), which has many species, is found on the surface of the 

 leaves and green stems of Dicotyledons and-a few Monocotyledons ; the much-branched 

 filaments of the mycelium spread over the epidermis, often crossing one another and at 

 the same time sending their suckers (haustoria) at many points into the cells of the 

 epidermis. The mycelia are reproduced by gonidia, which are abjointed in rows on 

 the summit of erect unbranched filaments (Fig. 65, /) ; these organs of propagation 

 are the only ones at present known in many species, as for instance in Erysiphe 

 (Oidiuni) Ttickeri, the Fungus which causes the grape-disease. In many others of the 

 Erysipheae the sexually produced fructifications are easily found ; filaments often grow 

 out of the rind of these fructifications which either lie close along the substratum like 

 the filaments of the mycelium, or stand up clear from it in various forms like a clothing 

 of delicate hairs. The fructifications and the gonidia are formed on the same 

 mycelium. 



The simplest mode of formation of fructifications is seen in Podosphaera. The 

 archicarps and antheridial branches are formed close together, and touching one 

 another from the first, at spots where the filaments of the mycelium cross (Fig. 65, 

 ///) ; both are small lateral branches ; the one that becomes the archicarp (c) enlarges 

 into an ovate shape and is delimited above its base by a transverse wall ; the one 

 that produces the antheridial branch (p) bends over the apex of the archicarp and 

 a cell is cut off there by a transverse wall. After 'fertilisation' has been effected, 

 filaments grow up from beneath the basal wall of the archicarp and also from the 



1 Baranetzky in Bot. Ztg. 1872, No. 10. 



2 Tulasne, Selecta fungorum Carpologia, I. Paris 1868. De Bary, Beitr. z. Morph. u. Phys. d. 

 Pilze, III, 1870 (Abh. d. Senckenb. Ges. zu Frankfurt a. M.) [Marshall Ward, On the 

 morphology and development of the perithecium of Meliola (Phil. Trans. Roy. Soc. 1883).] 



