370 BOTANICAL GAZETTE [MAY 
cells are quite small, cylindrical, hyaline, straight or curved, and 
do not differ markedly in structure from the abundant epiplasm of 
the young ascus. They grow for a time and become transformed 
into filamentous cells, the length of which varies in different species. 
When one of these cells approximates its maximum length, the 
upper end begins to enlarge and forms an ellipsoid portion into which 
the greater part of the protoplasm migrates. This portion then 
becomes cut off by a cross-wall and forms the fertile cell of the spore. 
The remainder constitutes the so-called primary appendage. 
Pleurage zygospora shows upon a superficial examination that the 
spores are developed after this same general method. 
Because of the peculiar interest attaching to this method of 
spore-formation, and also because of the great variability found to 
obtain in spores of Pleurage zygospora from collections made in the 
vicinity of Austin, Texas, the writer deemed it desirable to make a 
detailed cytological study of their complete development. The 
material for this study was grown in damp chambers on the natural 
substratum, and was prepared according to the methods employed 
in modern cytological technique. Flemming’s solution, weaker 
formula, as a fixing agent left nothing to be desired. The best 
stain was found to be the Flemming triple stain. Sections 10 4 
thick gave very good preparations for study. 
The immature perithecia contain many different stages in the 
development of the ascus, so that the stages could be studied in 
unbroken continuity in any one section. The study of fixed and 
stained material was supplemented by the use of fresh material 
crushed in water on the slide, and then treated with dilute aqueous 
gentian. violet or eosin glycerin. 
The details of nuclear division in the ascus and the young spore 
were not studied critically, as it did not appear that the material 
was favorable for a determination of the phenomena of chromo- 
some reduction.- The primary nucleus of the young ascus is quite 
large, and the chromatin material appears to be divided into four 
parts, but spindle stages were not observed (figs. 1-3). The 
cytoplasm is quite vacuolate, and this condition increases with the 
rapid enlargement of the ascus (fig. 4). After the ascus reaches 
about one-half its mature size, the division of the primary nucleus 
