4o8 
HARRY M. FITZPATRICK 
As the sterigma pushes outward, its tip is broad and rounded 
(figs. 43-45), but on reaching its full length it becomes acuminate 
(fig. 46). The production of a minute globose body at the tip marks 
the beginning of spore formation (fig. 47). This structure, termed the 
spore "initial" by Levine (32), gradually increases in size and elon- 
gates, the cytoplasm of the sterigma flowing out into it through the 
very narrow canal which results (figs. 48-56). While the young spore 
is forming at the tip of the sterigma the nucleus lies remote from this 
point. There is no evidence to show that it influences directly the 
formation of the spore "initial." As the cytoplasm flows outward the 
nucleus is carried along with it, and on reaching the narrow canal at 
the tip of the sterigma becomes greatly elongated, the diameter of the 
normal nucleus being many times that of the canal. The nucleus is, 
in fact, drawn out into a long rod, and all trace of the nuclear mem- 
brane is lost (figs. 51-54). The nuclear material at this stage stains 
deeply, and the rod has an irregularly beaded appearance. The size 
of the spore at the time of the entrance of the nucleus varies, but it 
has in most cases reached at least half its mature length. The nucleus 
after its entrance into the spore remains in some cases for a long time 
in the rod-like condition. Finally it contracts into an irregularly 
globose, homogeneous, deep-staining mass (fig. 55), which soon takes 
on a nuclear membrane and assumes the characters of a normal glo- 
bose, resting nucleus (fig. 56). The development of the narrow canal 
and the assumption by the nucleus of the irregular rod-like form recall 
similar phenomena described by Levine (32), Maire (36), Petri (44), 
Fries (13), and other workers for various higher Basidiomycetes. 
There is no reason to believe, however, that in Eocronartium muscicola, 
as in some of these cases, the centrosome is involved in forming the 
sterigma or in directing the course of the nucleus through the canal 
into the spore. The evident fibrillar strands which Levine (32) 
describes in Boletus as extending from the centrosome in the spore 
"initial" down through the canal to the definitely beaked nucleus 
in the basidium have no counterpart in Eocronartium. The passage 
of the nucleus into the sterigma is accomplished simply by the out- 
ward flow of the cytoplasm, and its passage through the canal into 
the spore is evidently of similar nature, no pull by kinoplasmic strands 
being exerted. In a unicellular basidium, as in Boletus, there is 
evidently need of a specialized apparatus for directing the course of the 
different nuclei into their respective sterigmata, since without such a 
