confluens and the Morphology of the Ascocarp. 325 
Darbishire has done, it loses all semblance of probability. 
Lindau ( 21 ) in his earlier work has recorded the existence of 
trichogynes for a considerable series of Lichen-species. His 
work, taken with Stahl's, Wainio’s, and that of the two 
authors discussed above, makes it certain that organs of this 
nature are of extremely widespread occurrence among the 
Lichens. In view of this mass of evidence the negative results 
of Krabbe, Fimfstuck (15) and others, must be regarded as 
having little weight. It is quite possible that certain genera 
or families of Lichens may be prevailingly apogamous or 
parthenogenetic, but that so definite and constant a structure 
as the ascocarp should be entirely different in its morpho¬ 
logical significance in these cases can only be established by 
positive evidence. It would be most remarkable if such 
complex structures as the trichogyne, carpogonium, and 
ascogenous hyphae could be present in Physcia and absent in 
Cladonia. At present there is no ground for the view that 
such apparently closely related forms as are the various 
genera of the ascus-bearing Lichens must be considered as 
morphologically unlike in such important parts as constitute 
the ascocarps, until the last detail of the nuclear phenomena 
in their reproduction has been worked out. So sceptical an 
attitude of mind is perhaps stimulative of research, but is not 
well founded, and its existence at present is simply due to the 
rivalry of opposing schools. 
Similar to Lindau’s hypothesis regarding the trichogyne, in 
the lack of evidence for its support, is Van Tieghem’s supposi¬ 
tion that the trichogyne constitutes an especial respiratory 
apparatus for the developing perithecium (37, p. 1166 ). This 
hypothesis has received sufficiently trenchant criticism by 
De Bary (13, p. 237 ) and need not be further mentioned here. 
For the Lichens in general there remains one difficult point. 
The spermogonia resemble very closely conidial fructifications, 
which in many Ascomycetes are plainly asexual reproductive 
organs. It is hence difficult, in cases in which the germination 
of these spores has not been satisfactorily tested, and the 
development of the apothecium has not been worked out, to 
