32 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
favorable for germination and the production of a new lichen indi- 
vidual. It may well be doubted whether such a combination is 
likely to come about often enough that among lichens spores may 
be regarded as important agents in reproduction. The chances of 
reproduction by spores were plainly decreased greatly when the sym- 
biotic relationship was taken on, and the result has in all probability 
been a considerable physiological degeneration of the spores in the 
course of phylogenetic development. 
SEXUAL REPRODUCTION. 
The sexual processes have not been studied in very many of the 
fungi most closely related to the lichens, but recent discoveries seem 
to indicate that sexuality is common there and in the ascomycetous 
lichens as well. In Collema, Stahl and others have found that the 
apothecium is preceded by an archicarp and a 
trichogyne (fig. 7), which are supposed to con- 
stitute a reproductive tract. The more recent 
researches of Baur, Darbishire, Lindau, and 
Wainio have proved the existence of similar 
tracts in lichens of several genera, and while 
there is yet much need of research regard- 
ing nuclear behavior, the general presence of 
sexual organs in lichens can scarcely be ques- 
tioned longer. 
The spermagonia have been supposed to 
constitute the male reproductive organs of 
. lichens, and Stahl thinks that he has estab- 
“lam, showing the arena lished beyond reasonable doubt that fertiliza- 
and the trichogyne. Enlarged tion actually takes place, the spermatia (fig. 3, 
a0 diameters. From Stabl. ¢, p. 16) from the spermagones (fig. 3, a) be- 
coming attached to the apex of the trichogyne, where a transfer 
of protoplasm occurs, Strangely enough, Moller, experimenting on 
lichens not closely related to Collema, has produced from the sper- 
matia thalli in all respects similar to those which he obtained from 
spores. This would seem to indicate that the spermatia, if they are 
sexual cells, have become so degenerate in certain lichens as to lose 
their sexual function, becoming capable at the same time of repro- 
ducing vegetatively. However, it is supposable that the spermatia 
may not be degenerate but capable either of f unctioning for sexual 
reproduction or of developing parthenogenetically. It seems neces- 
sary to add that some botanists regard the spermagones as bodies 
belonging to fungi parasitic on the lichen thalli. 
The question of the sexuality of lichens, together with that of the 
origin and development of the apothecium, has in the last half cen- 
tury excited quite as much interest as the one regarding the nature 
