4o6 
HARRY M. FITZPATRICK 
bipolar spindle, and at each pole the centrosome appears as a deeply 
staining point (figs. 35, 36). Astral radiations have not been observed. 
The chromosomes are somewhat elongated, rod-like bodies, and when 
they occupy the equatorial region can be counted with certainty. 
They do not scatter as they migrate toward the poles as in the con- 
jugate divisions, but are drawn apart in two well defined groups. 
The spindle at the beginning of the division is definitely intranuclear, 
but the nuclear membrane soon breaks down, and at late telophase the 
two groups of chromosomes lie free in the cytoplasm with indications 
of spindle fibers between them (fig. 37). 
The daughter nuclei soon round up, assume a definite membrane, 
and a nucleolus appears in each (fig. 38). At the completion of the 
mitosis the basidium undergoes rapid elongation, and the two nuclei 
migrate apart. The basidium soon attains its full length, and the 
nuclei enter the second mitosis. 
Few basidia have been found undergoing the second nuclear 
division, and it probably consumes far less time than the first. The 
spindle in this second mitosis is smaller than that in the first but 
resembles it in all other respects (fig. 39). The chromosome number is 
clearly four. The divisions in the two nuclei are not necessarily ex- 
actly simultaneous. In figure 39 the upper nucleus shows the two 
groups of chromosomes passing toward the poles, while in the lower 
nucleus the separation has not yet occurred. 
Before the completion of the second division a transverse septum 
begins to form near the center of the basidium, and when the daughter 
nuclei have rounded up the basidium is composed of two binucleate 
cells (fig. 40). When one of the nuclei resulting from the first mitosis 
divides more rapidly than the other, a second septum may be laid 
down in one of these cells before it appears in the other (fig. 41). 
Usually, however, these two septa are formed simultaneously so that 
the typical four-celled basidium results (fig. 42). Maire (36) figures 
and describes in Auriciilaria mesenterica similar cases in which the 
two septa last formed are laid down independently because of the 
more rapid division of one of the two nuclei. 
Comparatively few basidia in the preparations show stages follow- 
ing the spirem condition of the fusion nucleus, and preceding the four- 
celled basidium. It is evident that the mitoses are completed and 
the septa laid down in a relatively short space of time. Four-celled 
basidia which have not yet begun to form sterigmata are numerous in 
