Gilbert—Cyiological Studies of Lower Basidiomyeetes 391 
beneath the hymenial layer always contain two nuclei, and it is 
impossible at first to decide which cells are to function as basidia 
and which are to develop into paraphyses. 
The Basidium 
The young basidium may at first be smaller than adjacent 
cells, but this condition persists for only a very short time. The 
cell very rapidly elongates, and as the two nuclei fuse (fig. 12), 
it thickens and becomes two to three times the diameter of the 
paraphyses surrounding it. As soon as the nuclei have fused, 
often before the nucleoles have united (fig. 13), there is a rapid 
increase in size of the nucleus. No true resting period ensues, 
but a definite synapsis stage (figs. 14, 15) is soon observable. 
The chromatin material becomes distinctly massed at one end 
of the nucleus, and at this time it is possible to make out a dis¬ 
tinctly double nature of the chromatin elements. A heavily 
staining body is to be found on the nuclear membrane usually at 
the point where the chromatin is at its densest. Because of the 
association of this body (figs. 15, 16) with the chromatin, and 
because of its similarity to the centrosome which soon makes its 
appearance, this body has been taken to be the structure from 
which the centrosomes arise. It has not been possible to follow 
the method of development throughout, but this body is very 
evident during later synapsis and persists during the subsequent 
stages. The spindle is almost completely formed before the en¬ 
tire disappearance of the nuclear membrane, and the chromatin 
is massing at the center without, however, being in the shape of 
distinct chromosomes. The nucleole is pushed out beyond the 
spindle fibres and disappears in the cytoplasm with the break¬ 
ing down of the nuclear membrane (figs 17, 19). 
The chromosomes, because of their plastic nature, are not eas¬ 
ily counted, but four seems to be the number in the species 
studied (figs. 18-20). 
The daughter nuclei have a very short resting stage, and their 
division is quite similar to the preceding division (figs. 21, 22). 
The four nuclei now become arranged in a row in the rapidly 
growing basidium (fig. 23). The nuclei, however, soon begin 
to migrate slowly toward the apex of the basidium where the 
sterigmata are being formed (fig. 24). During this migration 
they decrease greatly in size and change in shape, becoming dis- 
