KrRKWOOD : POLLEN-FORMATION IN CUCURBITACEAE (237 
When by such manipulations the pollen-mother-cells of the 
same anthers were treated with different stains as well as those of 
different anthers and different fixation, the chances that the unusual 
structures observed in the cytoplasm are due to the reagents is 
minimized. 
SUMMARY AND CONCLUSIONS 
1. The development of the pollen was followed in several 
forms. In each case the layer of cells immediately below the 
epidermis in each anther lobe divides by a periclinal wall to form 
primary tapetal and primary sporogenous cells. The former 
again divide to form two or three layers in the wall of the pollen- 
_ Sac, the latter undergo repeated divisions in the case of Fevillea to 
= form a mass of pollen-mother-cells, but in Melothria, Micrampelis 
and Cyclanthera no such divisions were observed, In these fea- 
tures the development of the sporogenous tissue and the pollen is 
essentially the same as described for other members of the Cu- 
curbitaceae by Mirbel, Warming and others, and is in accord with 
_ the condition found in most of the seed plants. 
Be foe The division of pollen-mother-cells was given special atten- 
tion in Micrampelis. The principal feature of interest here is the 
_ Presence of certain darkly-staining, rod-like bodies in the cyto- 
plasm. These appear before the mother-cells have reached their 
: full size and persist for some time, gradually breaking up as the 
cell prepares for its first mitosis and appearing to resolve them- 
selves into many minute granules which stain darkly. These 
§ranules become more conspicuous between the first and second 
mitoses and gradually disappear as the spore approaches maturity. 
No evidence was gathered as to their function, though they seem 
to be of kinoplasmic origin. In this they are extranuclear in 
origin and are not derived from the nucleolus as has been observed 
in the case of Larix and some other forms. 
3. The cytoplasm appears to be distinctly fibrillar. In certain 
Cases the fibers of the reticulum are apparently stretched in lines 
tangential to the nucleus during the period of its rapid expansion. 
As the time of the first division approaches the cytoplasm presents 
the aspect of fibers radiating from the nucleus. The fibrillar 
aspect disappears with the formation of the spindle. 
