234 DIVISION II.— COURSE OF DEVELOPMENT OF FUNGI. 
capable of development. We may derive assistance also from analogies of cases 
which have been certainly ascertained; but these have only a subordinate value, 
for experience has certainly shown that sexuality is a phenomenon of irregular 
occurrence in the greater part of the vegetable kingdom, varying sometimes from 
species to species even in the higher plants, and hence homologies and analogous 
functions are here also not necessarily coextensive. 
According to these criteria the sexual organs of Pythium, for example, are 
really sexual, for the union of protoplasms is evident, and its necessity, though not 
demonstrable in strictly experimental manner by artificial separation and conjunction 
of the two parts, is all but absolutely proved by the fact that the union always takes 
place: but if we apply the same criteria to the homologous organs of the Sapro- 
legnieae the sexuality will at least be very doubtful. 
_ Similar results are obtained by the same method of determination in the case 
of.-the Ascomycetes in question. The protoplasms unite in Pyronema, and 
there is no exception to this rule; and as strict experiment is impossible, we 
may conclude, as in Pythium, with almost perfect certainty from the constancy 
of the phenomenon, that the union is necessary. The phenomena in Pyronerna 
-are so far different from those in Pythium that the archicarp grows to meet the 
male organ by means of a special organ, the /chogyne, and unites its protoplasm 
with that of the male organ; this union takes place after the trichogyne 
has previously been permanently delimited as a special cell by a transverse wall. 
These facts could hardly be understood but for the exact analogue presented by 
the majority of the Florideae. But these make it plain that the trichogyne is 
an organ of conception which first receives the fertilising matter, and that the 
effects of fertilisation are conveyed from it, in a manner which cannot be further 
considered here, to other parts of the female apparatus, which in the present case 
is the ascogonium. 
We are made acquainted with quite similar phenomena to those in Pyronema, 
though different certainly in form and more complex, from Stahl’s observations 
on the Collemaceae which have been described above. The most important 
complication arises from the fact that the male organs are spermatia detached 
by abscision, not antheridial cells formed beside the archicarp. The union 
with the trichogyne and the changes which proceed from the place of conjugation 
and affect the female apparatus which ultimately forms asci are very apparent. 
The necessity of the union for the further development of the female apparatus 
is in this case also not shown by strict experimental proof on account of technical 
difficulties ; but it is as good as certainly proved by the observation that not only the 
union of the spermatia with the trichogyne precedes those characteristic changes 
and developments, but that these do not take place if the spermatia for any reason 
have not made their appearance. 
We are met by the same arguments and results in the case also of Eurotium, 
though the facts observed in this case are not so striking at first sight as 
in Pyronema; and lastly Eidam’s observations on Eremascus show that the union 
of the protoplasms is as evident as it can be in organs which are extremely similar to 
those in question in Eurotium, Penicillium, &c. In these cases we may therefore 
affirm, that, according to our present criteria, the antheridial branches, or the 
