Lciboulbenia chaetopliora and L. Gynnidarum. 339 
similar series of conjugate divisions, but undergo no considerable growth, 
no branching, and no septation. 
The Ascus. 
Thaxter was the first to discover that the spores of the Laboul- 
beniales are invariably borne in sacs, and constantly to the number of 
four, or in a few species of eight. On these grounds he has unequivo- 
cally maintained their ascigerous nature. It has only remained to 
examine the spore-sacs cytologically (Faull, ’ 06 , ’ll) to prove the cor- 
rectness of his view, and to prove beyond question that they possess all 
the essential features of asci. 
They begin as basipetally arranged folds or outgrowths of the asco- 
genous cells. They are never septated off from the latter, but their bases, 
which at first are very broad, gradually contract until finally the cyto- 
plasmic connexion is broken. In Laboulbenia chaetophora the walls of 
the older asci are not always dissolved nor are the asci always completely 
sloughed off from the mother-cell (PI. XXXIX, Fig. 41), though both are 
common phenomena and are said by Thaxter to be characteristic for the 
group. 
At first small, the ascus grows to a relatively large size, during 
which time the definitive nucleus also increases enormously in bulk. 
The cytoplasm is finely granular and fairly uniform throughout. When 
mature there is a slight vacuolation in both the upper and the lower 
parts of the ascus (Fig. 51), and sometimes a few insignificant granular 
inclusions make their appearance. 
Two nuclei which we may with good reason assume to be lineal 
descendants of the pair that occupied the carpogonium in its later stages of 
development enter the young ascus and fuse with one another. Their 
chromatin is ordinarily distributed irregularly throughout the nuclear cavity 
in the form of a thread, an arrangement which persists for some time after 
fusion (f'igs. 43-5). Eventually a synaptic contraction sets in (Fig. 46) and 
the threads are matted to one side of the nucleus, though their connexion 
with the nucleolus is probably maintained. 
The synaptic stage is succeeded by one in which the threads are again 
loosely arranged, but this time much more regularly and with a more 
or less obvious relation to the nucleolus and an appearance of being paired. 
These features are clearly illustrated in Figs. 47 and 48. It will be seen, too, 
that there is a more or less regular system of achromatic threads radiating 
out from the nucleolus and traversing the entire nuclear cavity. 
The next stage is characterized by a very marked diminution in the 
apparent amount of chromatin, and by what may possibly be interpreted as 
a second contraction. Figs. 49 and 49 a represent the same nucleus from 
two consecutive sections, and are designed to show the entire amount and 
