CYTOLOGY OF EOCRONARTIUM MUSCICOLA 
407 
many of the sections. The nuclei in the four-celled basidium are all 
of the same size, and are considerably smaller than the fusion nucleus. 
The size varies little in different basidia and is maintained in the spore. 
Sterigmata and Spore Formation 
In the young condition the basidia stand at right angles to the 
surface of the sporophore and form a more or less definite palisade 
layer. During their elongation they fall over and assume a procum- 
bent position. An examination of mature basidia shows that the 
resulting bend usually takes place in the basal cell of the basidium 
(figs. 42-45) rather than in the hypha which bears it. This procum- 
bent position results naturally from the' lack of rigidity in the long, 
slender, flexuous basidium, but is nevertheless of decided importance 
in that it allows the sterigmata to arise at right angles to the surface 
of the sporophore unhindered by contact with neighboring basidia or 
sterigmata. The sterigmata are developed consequently in a palisade 
layer almost as well marked as that of the young basidia. In fact, 
when both young and old basidia lie close together, as is commonly 
the case, the palisade may be composed of a mixture of these two struc- 
tures. 
Each cell of the basidium gives rise to a single long, cylindrical, 
flexuous sterigma (figs. 44, 45), which bears at its tip an elongated, 
more or less crescent-shaped spore. The sterigma frequently reaches 
a length two-thirds that of the mature basidium, and has a diameter 
approximately the same as that of its nuclei. In rare cases sterigmata 
may arise simultaneously from all the cells, but far more frequently 
they originate independently of one another. In some cases the apical 
cell is the first to bud, in others it is the last. As the sterigma pushes 
outward, the cytoplasm in the cell behind becomes increasingly vacu- 
olate, and finally the basidium is entirely emptied. The nuclei in 
the various cells pass outward with the cytoplasm into their respective 
sterigmata. In some cases the nucleus passes out relatively early, in 
other cases it remains in the basidium until a sterigma of considerable 
length has formed. Before its passage outward it is globose, but in 
the tube it becomes somewhat elongated. This elongation is probably 
due in large measure to the stress exerted upon the membrane by the 
flowing cytoplasm. It is not due to the narrowness of the sterigma, 
since in some cases, in which marked elongation occurs, the diameter of 
the sterigma exceeds even the long diameter of the nucleus. 
