WEATHERWAX: SPIKELETS OF ZEA Mays - 487 
one who is familiar with the plant in its other interesting relations, 
Kuwada’s work, while of much value as far as it goes, is still 
incomplete. There is yet room for a great deal of interesting 
and profitable cytological work on varieties that have been inbred . 
for a number of generations, or whose genetic history is otherwise 
known for a long time. If from such work any regularity can be 
found for the different varieties, there will be afforded not only a 
probable basis for improving the present unsatisfactory systematic 
treatment of the genus but also a new field of study in correlations 
between cytological behavior and genetic results. 
The mature pollen grain is almost spherical; the exine is mi- 
nutely roughened, and there is a prominent germ pore (Fic. 8). 
The pore is surrounded by a thickened ring of intine and closed 
with a plate of tissue which resembles the rest of the wall in 
structure. The protoplasm is very dense, and careful staining is 
necessary to make the nuclei visible. The vegetative nucleus is 
irregular in outline and apparently does not have a definite mem- 
brane. The generative nucleus divides before the pollen is shed, 
forming the two long, slender sperms, which are pointed at the 
ends and usually crescent-shaped. 
It is possible that the development of the abortive pistil varies 
in some kinds of maize, especially some of the pod varieties that 
do not produce fruits in the tassel; but there is a remarkable re- 
gularity in all that I have examined. The organ develops as in 
the female flower—which will be described later—up to the time 
when the ovary wall should begin to be formed, but here it stops. 
Sometimes it is merely an oval or somewhat constricted protuber- 
ance (TEXT-FIG. 12), and sometimes there is a slight indication of 
the beginning of the ovary wall (W, TExT-FIG. 4). Ina few cases 
a large, conspicuous cell has been seen at about the place where 
the megaspore mother cell would be expected, but it is impossible 
to say at this time whether or not it develops this far. The disor- 
ganization begins while the epidermis is still intact and soon 
extends to many or all of the intercellular spaces (TEXT-FIGS. 12- 
15). The organ is usually completely consumed by the time of the 
differentiation of the pollen mother cells in the stamens of the 
same flower, and all that remains at anthesis is a small, shallow 
cup formed by the epidermis of the base of the aborted organ 
