CHAPTER V.—COMPARATIVE REVIEW.—-ASCOMFYCETES. 237 
A nearer approximation of the Ascomycetes generally, or of some of them, to the 
Florideae would not materially affect the conclusions at which we have arrived above 
with regard to the main questions connected with the homologies. 
In my first investigations (Beitr. III) into the development of the sporocarps in 
Erysiphe, Eurotium, Pyronema, and others I called the archicarps and antheridial 
branches generally sexual organs; and from the great amount of agreement between 
the sporocarps when fully formed I expressed the conjecture that all the Ascomycetes 
have homologous and analogous organs for the production of these sporocarps. 
Others followed me in this view, especially when they became acquainted with 
individual cases which confirmed it. The investigations which are here communicated 
have had the result of showing that my generalisation was incorrect, and that the mistake 
arose not merely from want of consideration of facts not then known, but more especially 
from not distinguishing sufficiently between morphological and phylogenetic homology 
and physiological analogy. I trust that I have taken this distinction sufficiently 
into account in my last special treatise (Beitr. IV) and in this work. 
Van Tieghem has been one of the chief opponents of my view, for he takes his 
ground on forms that have no distinct archicarps and does not allow of ‘sexuality’ 
in the Ascomycetes. His opinion briefly stated is this, that the differentiation of 
the ascogenous hyphae and their envelopes takes place at stages in the development 
of the sporocarp which vary according to the species, and that it occurs at the earliest 
possible stage in the species which are supposed to have sexual organs. The supposed 
female organ is only an ascogenous hypha differentiated at a very early period, the 
supposed male organs are simply part of the envelope-structures. The facts on which 
Van Tieghem originally founded his opposition were certainly not happily chosen. 
But if he is content to rest his case on Pleospora for instance, or even on the actual 
condition of things in Sclerotinia with which he has never been acquainted, he must 
be allowed to be quite in the right as against my original conjectural generalisation 
literally taken ; and if he objects that the actual sexual function of these organs has 
not been proved in the case of Eurotium and Podosphaera, he will find that this 
is allowed in my work of 1870. But Van Tieghem makes no enquiry into the 
homologies and extends his negation beyond the limits allowed by the facts. If 
he had duly considered the indisputable fact of the constant presence in Podosphaera 
of my antheridial branch, that is of an organ distinctly different from the later- 
formed structures of the envelope and accompanying the proper commencement of 
the sporocarp, he would have been led to those true subjects of enquiry which 
have been discussed in the foregoing pages, and which it has been attempted to elu- 
cidate; and the facts at present known about Pyronema, Eremascus and other forms 
should have led him to a different answer to his own enquiries. We need not go 
into his positive views with regard to the function of the organs in question, that, 
for instance, the antheridial branches serve to support the ascogonium and that the 
trichogyne in Collema is an organ of respiration, before it has been shown to be to 
some extent probable that the ascogonia are in danger of falling without this support, 
and that the particular organ in Collema is obliged to have an apparatus of its own 
to get air, and cannot respire without it quite as well as the elements of the interior 
of the thallus near which it is placed. Such fancies must certainly deserve the 
name of gratuitous hypotheses quite as much as the views which I have here 
explained. 
Another opponent of my ideas is Brefeld. He wavers between Van Tieghem’s views 
on the one hand’, and certain others, which, when stripped of some accessories which 
do not strictly belong to the question, agree with those of the present work?, I have 
therefore no reply to make, apart from the corrections of some matters of fact 

1 Bot. Ztg. 1876, p. 56, Abs. 23, and Schimmelpilze, IV, p. 142. 
2 Bot. Ztg. 1877, p. 371, and Schimmelpilze, IV. 
