596 Brooks .— The Development of 
associated in pairs (Figs. 20, 22). This state possibly indicates a conjugate 
condition of these nuclei, but in the absence of preparations showing nuclear 
divisions at this stage—apart from one doubtful case (Fig. 21), it is impos¬ 
sible to speak with certainty. In this doubtful case the difficulty of deter¬ 
mining the connexion of the cell in which it occurs prevents one from 
deciding whether this conjugate division is the one immediately before the 
formation of the young ascus or one at an earlier stage. The cells that con¬ 
tain the larger nuclei branch, and so the number of ascogenous cells is 
increased. Fig. 22 shows this branching. The ascogenous cells cannot be 
traced very far because of the intricate way in which all structures at the 
base of the perithecium are interwoven. Hence to follow the course of the 
ascogenous hyphae in Gnomonia is a more difficult matter than in Discomy- 
cetes generally. 
There is a considerable difference in regard to the manner in which the 
asci arise from the ascogenous cells. Crosier formation, so frequently 
described for other Ascomycetes, has been seen in Gnomonia also (Fig. 25). 
Often, however, although the end of the ascogenous cell begins to bend over, 
this process is not continued, and the terminal part, containing two nuclei 
which fuse, forms the ascus. Sometimes there is not even a trace of bend¬ 
ing over (Figs. 22, 23) before ascus formation. In Fig. 22 it is evident that 
the penultimate cell grows out laterally to form another ascus. The same 
process may no doubt go on indefinitely. This mode of ascus formation is 
similar to that described by Maire (26 a) in Galactinia succosa. Faull ( 14 ) 
has also pointed out the differences to be observed in the mode of ascus 
formation in other Ascomycetes. 
The two nuclei present in the young ascus cell lie in contact with each 
other and soon fuse together (Fig. 27). They seem to melt into each other. 
The nucleoli, however, do not become united for some time. Immediately 
after fusion, the nucleus thus formed increases in size and the ascus grows in 
length. 
It should be mentioned here that while the first asci have been in pro¬ 
cess of formation, the neck of the perithecium has been differentiated by the 
outgrowth of cells which originally formed the part of the coil towards the 
trichogynes. The periphyses develop as narrow outgrowths from cells 
on the inside of the upper part of the ascocarp. As stated earlier, no 
typical paraphyses are developed. 
The Cytology of the Ascus. 
When the ascus nucleus has reached its maximum size, i. e. shortly 
after fusion has taken place, the chromatin thread becomes densely aggre¬ 
gated towards one side of the nuclear membrane (Fig. 28). At a later stage 
the thread becomes looser and more generally distributed. It has been 
