The individuality of the chromosomes and their serial arrangnient, etc. 121 
In the nuclei of cells situated in the outer layers of the root cap and 
in stUl older portions of the root the chromosomes cannot be identified. 
In the dying cells of the root cap the nuclei decrease in size, the nucleoles 
become smaller and the nuclear cavity becomes filled with a dense granulär 
substance which stains quite uniformly. 
The Sporogenous Tissues, 
Everywhere in the ceUs of ovary walls, styles, Stigmas, filaments, 
tapetum, and sporogenous tissue the chromosomes are recognizable in 
the resting nuclei. They are especially conspicuous in the tapetal nuclei 
as shown in figure 3, in the nuclei of the filaments (fig. 7 b), and in the 
nuclei of cells in the walls of the ovary (fig. 2). These nuclei are as a 
rille smaller than those of the root tips and accurate counts of such large 
numbers of chromosomes is not possible, but it is clear that the number 
of chroniatic units does not exceed the chromosome number and that 
there is never a completely reticiilated condition of the chromatin. 
The resting nuclei in the archesporial ceUs of the young stamens 
ränge from 4,0 a to 5,25 /.i in diameter and are hence slightly smaller 
than the root tip nuclei. In the prophases of dmsion, however, the 
nuclei often increase in diameter to 8,0 or 8,25 a which is shghtly greater 
than the diameter of the nuclei in the root tip during the same stage. 
A cross section through a loculus at the stage of the early divisions 
of the archesporial cells shows that there it consists of a single outer 
layer of cells forming the wall, two rows of tapetal cells, and a single 
circle of wedge-shaped sporogenous cells. In such a section four or five 
sporogenous cells are usually shown. They are closely crowded together 
and are wedge-shaped in cross section with the apices in the center. The 
diameter of the entire cylinder of spore producing tissue at this stage 
is about 17 to 20 
The Heterotypic Division. 
When the spore mother-ceUs are fully fornied and are passing into 
synapsis, five or six appear in a cross section of a loculus and the diameter 
of the whole cyhnder of cells is from 22 to 25 fi. In the resting nuclei 
of the spore mother-cells the chromosomes are situated at the periphery 
and appear as shown in figure 19. In the presynaptic stages the nucleus 
enlarges to about 6,5 or 7,5 in diameter. The chromosomes draw 
away from the nuclear membrane appearing as in figure 20. They are 
now fusiform, which is due apparently to a sort of spinning out of their 
