Sperm-Cells in Asclepias Cornuti , Decaisne. 135 
The outer wall of the pollinium-cells consists of part of the 
wall of the mother- cell together with the cross walls formed 
by the division of the mother-cell. Neither the pollinium- 
cells nor the tetrads (as in Orchidaceae *) ever become free, 
but form the pseudo-tissue known as the pollinium, a condition 
similiar to that described by Rosanoff (1865) for Mimoseae. 
As they enlarge, these cells press upon each other and thus 
assume various shapes (Figs. 24-26, 32, 34), and the radial 
arrangement also becomes obliterated at last (Fig. 34). At 
places where the cytoplasm has shrunken slightly from the 
outer wall it is easy to see that a delicate inner membrane has 
been formed (Figs. 23-25). 
At a very early stage, there appear in the cytoplasm 
clearly defined circular areas of rod-shaped bodies which 
stain very densely like chromosomes (Figs. 24, 25). In older 
pollinium-cells these bodies become more and more distinct 
(Fig. 26) and the oval spaces containing them seem to be 
delimited by a distinct membrane, though whether or not this 
is more than the surface film of the cytoplasm may be a 
question. Such a condition as that shown in Figs. 28-31 
seems to indicate that there is a true membrane developed 
here about a vacuole in which are the rod-shaped bodies. 
These areas suggest the nuclear-like bodies described by Juel 
(1900) for Syringa rothomagensis , but of course it can be 
only a similarity in appearance, for Juel’s interpretation is not 
at all probable for the condition found in Asclepias. These 
rod-shaped bodies gradually disappear as the pollinium-cells 
develop, and this suggests that their function is nutritive. 
They often descend into the pollen-tube, but have never 
been found to travel as far as the micropyle. It is pos- 
sible that the disappearance of so large a percentage of the 
nucleolar substance of the primary pollinium-cell may have 
some connexion with the appearance of these bodies. The 
writer purposes to study them further as soon as fresh material 
again becomes available. 
1 Guignard (1882), p. 35. 
