DEVELOPMENT OF PISTILLATE CONES. yA | 
At the time of pollination in January the prothallus forms a spher- 
ical mass of soft, watery, rapidly-developing tissues in the middle of 
the nucellus which still comprises a considerable thickness of tissue 
on each side (fig. 1). No trace of the archegonia can yet be dis- 
covered. 
The ovule at this time has reached only about one-third of its mature 
width and length, and growth in the size of all organs continues for a 
considerable period following pollination. The prothallus grows in 
size proportionately more rapidly than the other organs, and this is 
accomplished largely at the expense of the nucellus, which gradually 
becomes thinner throughout, and is finally, at the time fecundation 
occurs, found to be compressed to a very thin membrane at the apex, 
and below on the sides and base has largely split up into very thin 
shreds, seldom being found as an unbroken membrane throughout. 
The archegonia are differentiated in the upper part of the prothal- 
lus shortly after pollination, but do not reach their mature size until 
a short time before fecundation, which does not occur until four 
months later. Four archegonia are almost universally formed in each 
prothallus, but some instances have been observed where a fewer 
(2 or 3) or a larger number (5 or 6) have been developed. 
During the increase in size of the archegonium through the months 
of March, April, and a part of May, the nucleus of the central cell 
remains in the upper part of the cell near its point of reorganization 
after the preceding division, which gave rise to the neck cell (fig. 10). 
It is usually elliptical and very large in comparison with the nuclei 
of surrounding cells. This location of the nucleus during the main 
growth period of the central cell of the archegonium is evidently 
common in related plants until after the ventral canal cell is cut off. 
Treub described the same location in Cycas circinalis (117), Ikeno in 
Cycas revoluta (65), Hirase in Ginkgo (59), Blackman in Pinus sylves- 
tris (16), and Murrill in Zsuga canadensis (91; p. 587). 
The protoplasm of the central cell during the latter part of this 
period of growth in size presents the most beautiful foam structure 
the writer has ever observed. 
Shortly before fecundation the nucleus of the central cell divides 
and a small cell is cut off at the apex, which corresponds to the ven- 
tral canal cell of the conifers. Until the publication of Ikeno’s pre- 
liminary note announcing the discovery of this canal cell in Cycas 
revoluta (65) it had been supposed that it was not formed in the 
Cycadacee. It would seem, however, from its occurrence in Cycas 
and Zamia that it is probably as generally formed in the Cycadacez 
as in the Conifere. Hirase has also recently described the formation 
of this cell in Ginkgo biloba (59). 
The writer has not observed the division of the nucleus leading to 
the formation of the canal cell in Zama, but the process probably cor- 
