Generations , and General Cytology of the Uredineae. 349 
of lichens can develop as conidia, but, as pointed out by E. Fischer (Bot. 
Zeit., 1888, p. 158) in reviewing Moller’s work, and also later by Harper 
(20), this in no way proves that the spermatia are not potential male 
cells. That they do not usually develop except in nutritive solutions, that 
it is often months before they germinate, and that their growth is ex- 
cessively slow, strongly suggest that they are not simple conidia ; but 
these facts are quite in keeping with the view that they are male repro- 
ductive elements. The suggestion lately put forward by Metzger (33) — 
that the spermatia of lichens are male cells which have retained a certain 
power of vegetative development, and, now that in many cases the 
ascus fruit develops without their aid, they sometimes act as conidia, and 
may have become modified in that direction — seems to be the most satis- 
factory one 1 . 
There seem to be no data for a comparative cytological study of the 
spermatia of lichens, though it would be of great interest. The figure of 
the spermatium of Buellia punctiformis given by Istvanffi (24) shows a cell 
with a much smaller nucleus in proportion to the size of the cell than in the 
Rusts ; but it is possible that only the nucleolus was observed. 
FERTILIZATION IN THE AECIDIUM AND THE NUCLEAR 
FUSION IN THE TELEUTOSPORE. 
It is very clear that the process which takes place in the young cells of 
the aecidium of P. violaceum is one which has most of the characters of an 
ordinary sexual process. A cell is to be observed, which after cutting off 
a sterile cell above, increases in size and becomes a specialized reproductive 
cell, exhibiting abundant protoplasm and a large nucleus with a well-marked 
nucleolus. A pause then occurs in its development, but it is later stimulated 
to further growth and rapid division by the entrance of a nucleus from 
without. 
Such a series of phenomena leave no escape from the view that the 
fertile cell is a female reproductive cell which undergoes a process of 
fertilization. There are, however, two points in which the process differs 
from that of ordinary fertilization. One is, that the two nuclei which 
become associated in the fertile cell do not fuse, but retain their morphological 
individuality, though the closeness of their relationship is shown by their 
always dividing together in close juxtaposition ; a fusion of nuclei does 
ultimately take place in some of their descendants, but it is confined to 
those pairs of nuclei which are to be found in the teleutospores. The second 
point of difference is, that the entering nucleus is derived from an un- 
1 Hedlund (22) has described two cases in which the spermatia of lichens germinated and 
developed a thallus in a state of nature. 
