Sands—Spore Formation in Microsphaera Alni. 735 
tow becomes an ascns in which the two nuclei fuse. In the 
absence of observations concerning the origin of the entire as- 
cocarp, it is as yet premature to> draw conclusions as regards 
the significance of the fusion in the ascus in this case; how¬ 
ever, one cannot avoid a suspicion that possibly antheridial and 
oogonial nuclei are formed but do not fuse in the oogonium^ 
remaining separate and passing by conjugate division through 
the asoogenous cells until they reach the ascus where the fu¬ 
sion occurs. The process in this case would then at least be 
conspicuously similar ' to that in the rusts as described by 
Blackman (2) and Christman (3). 
The first of the three nuclear divisions in the ascus is des¬ 
ignated as heterotypic, being characterized by synapsis and a 
double longitudinal division of the chromosomes. The second 
division, in which eight protochromosomes appear which later 
form four double chromosomes, he regards as homoeotypic, and 
the last division as typic. Thus Maire agrees with the view 
many times expressed that the ascus is a spore mother-cell com¬ 
parable to the spore mother-cell of a moss or fern. 
The achromatic part of the division figures has both an in¬ 
tranuclear and an extranuclear origin. The center appears on 
the interior of the nucleus but against its membrane, at the 
summit of an intranuclear aster. The center divides, the two- 
halves move in opposite directions, and a spindle is formed be* 
tween them on which the chromosomes are arranged. Radia¬ 
tions are meanwhile formed in the cytoplasm about the elon¬ 
gating nucleus as a center, which become more prominent at 
its two ends and finally, form the polar asters of the completed 
spindle. The asters and spindle are thus of different and in¬ 
dependent origin. The eight nuclei become beaked, and Maire 
holds that spore formation is effected in the manner described 
by Harper. 
Guilliermond (7, 8) has also investigated Pustulariw vesictdo- 
sa and Galactinia succosa , studied by Maire, as well as Peziza 
Catnius , P. rutilans and Aleuria cerea , and he corroborates 
many of Maine’s observations, differing from him, however, 
