78 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
advent of an ascus according to this investigator, was the appearance 
of four nuclei in a recurved tip of an ascogenous hypha. Next, by 
means of transversely placed walls, these nuclei were separated from 
one another so that one lay in the end, two in the second cell, the 
curved portion of the hypha, and the fourth in the third cell. The 
ascus grew out from the second cell, the two nuclei of which fused, 
resulting in a uninucleate condition of the ascus, the earliest stage 
observed by De Bary. Dangeard at first maintained that the ascus 
grew out from the point of junction of two hyphal threads, which 
he supposed to be male and female organs respectively. Subse¬ 
quently he discovered that there was no such fusion, but that the 
phenomena are such as I have just described. 
Harper (: 00) has verified Dangeard’s observations in Pyroneyna 
confluens. He has shown further that there are at first two nuclei 
in the recurved tip of an ascogenous hypha, that these divide mitotic- 
ally and synchronously to form the four observed by Dangeard, and 
that one of each pair of daughter nuclei is relegated to the young 
ascus. Harper has also confirmed the work of Gfjurasin, but his 
most important work began where Gjurasin’s left off. His main 
problem has been to determine the exact process involved in the 
delimitation of the plasma of each spore. He has investigated the 
origin of the spores in Erysiphe communis , Pezizct vesiculosa , 
Ascobolus furfuraceus (Harper, "97) Lachnea scutellata (Harper, 
’99), and Pyronemci coyifluens (Harper, : 00), and has concluded that 
the process is practically the same for all of the Ascomycetes. 
According to Harper this process is a distinctly unique one. The 
first step consists in the formation of a beak by each nucleus. This 
beak bears at its extremity the persistent centrosome and astral rays. 
The astral rays next swing outwards and down, the uppermost com¬ 
ing into contact laterally and fusing into a thin membrane. At this 
stage as far as relative positions are concerned, the membrane bears 
the same relation to the nuclear beak that the cover of an opened 
umbrella does to the rod that supports it. This “ kinoplasmic 
membrane continues to grow downward. Eventually it curves 
inward, the edges meet at a focal point, and the process of delimi¬ 
tation is complete. There has been no aggregation of protoplasm 
about the nucleus, but the membrane of fused astral rays, the plasma 
membrane of the young spore, literally cuts the spore plasma out of 
a homogeneous mass of protoplasm. 
