CHAPTER V.— COMPARATIVE REVIEW. — ASCOMYCETES. 25 1 



substances ; thus we get resting gonidia, resting gemmae, and resting mycelia, the 

 latter often appearing as torulose filaments or crust-like masses. All the gonidial and 

 resting forms are capable of germination under favourable conditions, and all the forms 

 included in divisions I, 2, and 3 may be changed into one another if the conditions of 

 growth are suitably varied. 



We must not enter here into the question whether Fumago has other organs of 

 propagation besides the perithecia which are said to occur and those which may 

 possibly occur, though it is one which may very well be asked after Tulasne's account 

 of F. salicina 1 . 



Section LXXIII. It is almost to be expected in the case of pleomorphous 

 species of Ascomycetes, that only separate members of their form-cycle should often 

 be found on a substratum at any given time, whether ascocarps or gonidio- 

 phores or gonidial receptacles. The frequency of this occurrence in a particular 

 species will depend on the ease with which it spreads as a rule over different kinds 

 of substrata under a great variety of external conditions, and on the other hand, also 

 on the strictness with which it is tied to special conditions of vegetation, in order to 

 produce the particular member which closes the cycle. Examples are seen in the 

 species of Fumago, Pleospora, and Penicillium, and in Sclerotinia Fuckeliana which 

 have been described above ; the mycelia of these Fungi bearing simple gonidiophores 

 are of universal occurrence in the form of Moulds, and they are propagated in the same 

 form, while the sporocarps are much more rarely found ; the conditions under which 

 they occur in the first two genera are not yet precisely ascertained 2 ; in Penicillium 

 they are produced on plants artificially grown on bread and spontaneously on the 

 skins of grapes that have been pressed for wine, and in Sclerotinia Fuckeliana only 

 on sclerotia which have developed and arrived at a certain degree of maturity on 

 particular foliage-leaves (Vitis, Castanea, Quercus) ; a large number even of the 

 sclerotia of this species produce only new gonidia, as is especially the case with those 

 which are so common on dead cabbage-stalks, the Sclerotium durum of old writers. 

 The majority of known species which form gonidia behave in a similar manner ; 

 the converse proceeding, a comparatively copious formation of sporocarps with 

 scanty production of gonidia, is comparatively rare, though it does sometimes occur, 

 as in Melanospora parasitica. Many or indeed most of the gonidial forms of species 

 that are now better known were for these reasons described as form-species, before 

 their genetic relations had been ascertained, and were distributed into corresponding 

 groups, the pycnidia and spermogonia being arranged in the Sphaeropsideae, 

 Cytisporeae, and Phyllosticteae s , the simple hyphal gonidiophores and open hymenial 

 layers in the Hyphomycetes, Haplomycetes, and Gymnomycetes of Fries. Proof of 

 this statement is to be found in the special descriptive literature, to which reference 

 here is unnecessary, since the historical facts are of the same kind as those to 

 which attention was called above in the case of the Mucorini, Peronosporeae, and 

 other forms. 



Another fact which was noticed in the description of those groups is also 

 repeated in the Ascomycetes, namely, that there are forms which strongly resemble 

 the members of the development of thoroughly well-known species, some even 



1 Tulasne, Carpol. II. ' ; Ibid. 3 Fries, Summa Veget. Scand. II. 



