82 SPERMATOGENESIS AND FECUNDATION OF ZAMIA. 
have undergone no perceptible change. Zamia material in good con- 
dition for demonstration and for careful study of the details of sper- 
matogenesis and fecundation can thus easily be obtained by any of the 
universities in Eastern United States. The comparative dates of 
development of different stages is given in the paper. 
(3) Pollination is accomplished by the wind. The scales of the cone 
gradually reflex from the base upward in regular sequence, leaving an 
opening about one-fourth of an inch wide between the scales when fully 
open, into which the pollen must be blown to cause fecundation. 
When blown into the cone in this way it naturally rattles down to the 
axis of the cone near the micropyle of the ovary. In the further 
process of pollination a mucilaginous fluid is evidently extruded, which 
catches the pollen grains and is later drawn into the pollen chamber 
at the apex of the nucellus, either by absorption or by suction created 
by the breaking down of the tissue in the formation of the pollen 
chamber. In this way the pollen grains come to lie in the pollen 
chamber at the apex of the nucellus, where they germinate and form 
the spermatozoids. 
(4) The mature pollen grain has two small prothallial cells cut off on 
one side of the grain, which are developed while the grain is still in the 
pollen sac.. Indications of a resorbed prothallial cell have been 
observed in mature pollen grains and in grains shortly after germina- 
tion. While the development of the pollen grain has not been followed, 
and the matter 1s somewhat doubtful, yet it is believed that three pro- 
thallial cells are cut off occasionally, if not regularly, the first of which 
is uniformly resorbed, as in the case of Ginkgo and Pinus. The two 
cells which remain plainly evident in the pollen-grain cells are referred 
to as the first and second prothallial cells, in the order of their formation. 
(5) In the development of a stalk cell and central cell (generative 
cell or A6rper cell) Zamia is found to correspond very closely to the 
Conifer as described by Strasburger and Belajeff. The general proc- 
ess Is obscured, however, by the early development of the prothallial 
cells before the division of the second prothallial cell occurs. The first 
prothallial cell early begins to arch out into the second prothallial cell. 
As the development progresses this continues till the second prothallial 
cell comes to surround the main body of the first prothallial cell. The 
division of the second prothallial cell occurs after this condition is 
formed and the lower end of the spindle is crowded to one side by the 
intruding first prothallial cell. ‘When the wall separating the stalk 
cell and the central cell is formed it is located near the apex of the first 
prothallial ceil, so that the puzzling appearance of a cell surrounding a 
cell is formed. The nucleus of the stalk cell is always crowded to one 
side by the first prothallial cell. The writer has found the same proc- 
ess of development to occur in Ginkgo also. 
(6) Shortly after the completion of this division the blepharoplasts 
