POLLINATION IN THE PINE 
LANTS which depend on the wind have presented an impenetrable ex- 
for fertilization must necessarily terior. At the base of each scale 
have pollen adapted to travel by are two _ ovules, not enclosed in 
air. Ifa plant regularly depends 
on bees or other insects to carry its 
pollen, the pollen-grains are likely to 
be sticky and fairly large. If, how- 
ever, the pollen must be transported by 
the wind, then the grains must neces- 
sarily be as light as possible and some- 
times, as in the pine, they are furnished 
with wings or air sacs to buoy them up. 
So equipped, pollen grains can travel 
almost incredible distances. Engel- 
mann, a careful and trustworthy ob- 
server, reports: 
“The property of the pine pollen to 
float for a long time in the air, and to 
be carried by storms to very distant 
localities, is well known. I have found 
in streets of St. Louis after a rainstorm 
from the south, in March when no 
pines north of Louisiana were in bloom, 
pine pollen which must have come from 
the forests of Pinus australis on Red 
River, a distance of about 614° of 
latitude or 400 miles in a direct line.”’ 
The male and female flowers of 
the pine are quite distinct, as will be 
seen from Fig. 8, but are borne on 
the same tree. The male cones appear 
in the eastern United States late in 
the fall, lie dormant through the winter 
and ripen their pollen in the spring, the 
pollen being ready for dispersal in May 
or June. In March or April the female 
cones can be distinguished; they develop 
rapidly until they are mature at the 
same time as the male cones. 
At about the time that the staminate 
flowers are launching their clouds of 
glistening pollen on the wind, the axis 
of the female cone elongates, thus 
forcing open the scales, which hereto- 
fore have been pressed together and 
1In Trans. St. Louis Academy, Vol. IV, p. 159, 
402 
FECUNDATION OF THE OVULE 
The ovule or egg-cell of the pine (P. austri- 
acus) is here photographed, immensely 
enlarged, about one year after it was 
pollinated. The pollen grain has lain 
dormant within it for that length of 
time, but is now beginning the actual 
fertilization. In the center of the egg 
can be seen the large maternal nucleus 
at the top of which the functional male 
nucleus has made a deep depression—a 
feature characteristic of the pines. 
Very shortly it will enter the egg- 
nucleus at this point and the two 
nuclei will unite, bringing together the 
hereditary material which each carries 
and thus starting the development of a 
new tree. At the upper end of the ovule 
a large vacuole is seen as a clear spot, 
to the left of which is the second 
male nucleus, which takes no part in 
fecundation. Photo-micrograph from 
David M. Mottier, Bloomington, Ind. 
(Fig. 7.) 
