CHAPTER V.—COMPARATIVE REVIEW.—ASCOMYCETES. 251 
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 al che forms 
included in divisions 1, 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!. 
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’; 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 *, 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. 2 Ibid. ® Fries, Summa Veget. Scand. II. 
