STUDIES OF THE DEVELOPMENT OF PEPEROMIA HISPIDULA 335 
tenth of the nuclear cavity (figs. 38, 39). As the nucleus emerges 
from synapsis some of the constituent chromatin threads are loosened 
up, thus again becoming visible. Some portions of the thread are 
distinctly beaded (fig. 40). This loosening up of the chromatin thread 
continues till, from the synaptic knot, a slender, beaded, loosely coiled 
spireme is formed, which lies chiefly near the periphery of the nuclear 
cavity. Some loops of this spireme are evidently double (fig. 41). 
From this time onward the spireme thickens, and where the beading 
is at all distinct, the chromatin masses are evidently larger. Figure 
41, for example, is of a nucleus the thick spireme of which is evidently 
just about to segment into chromosomes. In the other sporangium of 
the anther from which the latter figure was drawn the mother-cell 
nuclei had already divided. 
There is nothing peculiar about the spindle formed in the two divi- 
sions of the nucleus of the microspore mother-cell. The chromosomes 
of the first division are about i ju thick and 2 or 3 /a long, and are bent 
to U-shaped or V-shaped bodies so that it is difficult to count them with 
certainty (figs. 42, 43). The character of the chromosomes before and 
during this division was not made out in sufficient detail to demonstrate 
the occurrence of a true reducing division here. The two chromosome 
groups resulting from this first division become organized into definite 
nuclei, with a distinct nuclear wall and a coarse peripheral net of 
chromatin. In the latter there can often be distinguished about 14 
larger chromatin grains or masses which range from a half ijl to one 
fx in thickness (fig. 44). Remains of the first spindle are clearly 
seen even at this stage. The chromosomes formed at the second 
division are 12 or 14 in number, and are at first much more rounded 
than those of the first division. Even when they move toward the 
poles these chromosomes are but slightly elongated and not much 
bent. The spindle of this second division persists, and by it, together 
with the remains of the spindle of the first division, the four spore 
nuclei, when first formed, are connected together (fig. 45). 
The microspores of the tetrad are cut out in the usual manner, and 
the nucleus of each shows then a well-developed, fine-meshed chromatin 
net (figs. 46, 47). By the time the tetrahedral spore has rounded out 
to a globular form, and before theexine has become much thickened, 
the nucleus of the pollen grain divides to two (figs. 48, 49). One of 
these two nuclei soon becomes twice the bulk of the other (fig. 50). 
The larger, probably the pollen tube nucleus, lies nearer the wall of 
