132 Gager . — The Development of the Pollinium and 
as necessary an antecedent to the second division as to the 
first. If the interpretation suggested above should prove to 
be correct for Asclepias , it could not be considered as the 
function of the nucleolus in all plants, for the nucleolus is 
sometimes present after the spindle-fibres are formed 1 . 
The mature primary pollinium-cell is shown in Fig. io. In 
this stage the nucleolus stains very slightly, if at all, with the 
gentian-violet, while the nuclear reticulum takes a deep blue 
colour. There is a well-defined nucleolar membrane, and the 
slightly vacuolated cytoplasm contains many granules evenly 
distributed throughout and stained with the gentian. These 
granules first appear at a much earlier stage (Fig. 9), but 
disappear as division approaches. 
The First Division of the Primary Pollinium-Cell. 
After attaining the maximum size, the primary pollinium- 
cell passes a comparatively long period during which it under- 
goes no visible changes. Stevens refers to this as a period of 
rest. The first indication of approaching nuclear division is 
the contracted condition of the linin network to one side of the 
nucleolus, first described by Moore ( 1894 ) and later by others, 
and known as synapsis. The network does not appear to be 
wrapped about the nucleolus either in whole or in part during 
this stage. Immediately preceding this condition, the granules 
on the linin network are more prominent and stain more 
deeply with the gentian-violet, while the nucleolus takes the 
gentian only slightly, if at all. During synapsis the network 
does not takes the gentian, while the nucleolus stains a deep 
blue. There is no reason for considering synapsis in Asclepias 
as other than a normal condition. 
The nucleus is too small for an accurate determination of 
the finer cytological phenomena at this or at later stages of 
division. After synapsis the reticulum opens out (Fig. 12), 
and stains deeply with the gentian, while the nucleolus stains 
less deeply than during synapsis. Fig. 16 shows what is 
1 e. g. in the generative cell of Pinus. Ferguson (1901). 
