130 Gager , — * The Development of the Pollinium and 
as tapetal cells, as described by Caldwell (1899). The 
multiplication of nuclei characteristic of tapetal cells takes 
place in this layer as shown in Fig. 7. After the pollinium 
becomes mature, the cells of the tapetum disintegrate. 
The Primary Pollinium-Cells. 
The young primary pollinium-cells now pass through an 
extended period of growth, elongating greatly until they are 
from four to six times as long as broad. They are oriented 
with the long axis radial as described by De Mirbel 1 (1833) 
for Cucurbita , by Juel (1900) for Car ex acuta , and as first 
described by Schacht (1853) and later by Stevens (1898) for 
Asclepias. The nuclei increase in size and the nucleolus, 
which often occupies over one-half of the nuclear cavity, stains 
deeply with gentian-violet. 
About this time also, from one to two little wart-like bodies 
appear at the edge of the nucleolus, similar to those described 
and figured by Wiegand (1899) for Potamogeton , and inter- 
preted by him as probably the true nucleoli. I could not 
make out any constant difference in the staining reaction of 
these little bodies and the large one to which they are 
adjacent, as described by him. In Fig. 9 two of these bodies 
are shown for each nucleolus, and in Fig. 10 there is only one, 
while in P'ig. 11 , which is a later stage, there are none. 
Figs. 13 and 14 , which represent sections through the 
nucleolar structure of the pollen-mother-cell, suggest that 
in Asclepias , at least, these wart-like bodies are a stage in 
the fragmentation of the nucleolus. Fig. 13 suggests that 
five bodies have been given off from the large one, and, if this 
is the correct interpretation of the condition there figured, it 
is probable that Figs. 13 and 14 represent successive stages in 
this division. From the later condition shown in Figs. 12 and 
16, it seems probable that this fragmentation of the nucleolus 
does not always take place. Associated with this phenomenon 
of growth and fragmentation, is a more or less vacuolated 
1 Quoted by Nageli (1842), p. 7 . 
