Nichols, A morphologicai study of Juniperus communis var. depressa. 213 
the wall of the spore (figs. 40— 42). This cell is at first lenticular, 
but toward the close of the summer it rounds out and becomes 
spherical, thus separating more or less from the spore wall. The 
male gametophyte passes the winter in the condition represented 
by fig. 43. 
Activity recommences early in the spring when the tnbe 
nucleus moves down toward the tip of the pollen tube (fig. 44), 
where it becomes surronnded by a dense mass of cytoplasm. The 
lower portion of the pollen tube now undergoes a marked increase 
in size, enlarging in all directions at the expense of the adjacent 
sporophytic tissue, but there is no marked growth in length until 
after the division of the generative cell which occurs late in April. 
Fig. 45 shows the spirem of the division by which the stalk 
and body nuclei are produced, but none of the later phases were 
seen. The division is consummated very rapidly. Fig. 46 is drawn 
from a pollen tube in the same pollen chamber as that from which 
fig. 45 is taken and represents the two resulting nuclei. The 
smaller of the two is the nucleus of the body cell, the larger is 
the stalk nucleus. The phenomena which follow the division of 
the generative cell in the conifers present certain differences, as 
described by various writers. Belajeff (1893) and Strasburger 
(1892) report that in J. communis and Thuja respectively two 
cells of unequal size are formed, the larger of which, the stalk 
cell, degenerates. Coker (1903b) describes a similar condition in 
Taxodium. In Sequoia (Lawson 1904 a) and in Saxegothaea 
(Noren 1907), on the other hand, immediately after the division 
of the generative cell the nuclei of the stalk and body cells lie 
free in a common cytoplasm. In Sequoia the body nucleus soon 
becomes invested with a dense zone of cytoplasm and develops a 
distinct membrane, but at no stage is there a distinct stalk cell. 
The observations of the writer show that in the species studied 
the two nuclei likewise at first lie free in the cytoplasm of the 
tube, and that a true stalk cell is not formed. Doubtless a closer 
examination of this phase in other Cujpresseae will show similar 
conditions. 
Very soon after their formation the stalk and body nuclei 
pass down toward the tip of the tube, the stalk nucleus usually 
in advance. The tube nucleus, which has meanwhile wandered 
back toward the upper end of the tube, meets the two nuclei about 
midway, and they pass down the tube together (fig. 47). The 
three are easily distinguished at this period, the stalk nucleus being 
somewhat larger than the body nucleus and slightly smaller than 
the tube nucleus, while there is usually a similar difference in the 
size of their nucleoli. By the time they have come to rest in the 
swollen tip of the tube, the body nucleus has become surrounded 
by a dense zone of cytoplasm and is cut off from the surrounding 
protoplasm by a definite membrane (fig. 48). Concomitantly with 
this condition in the male gametophyte, the megaspore, which has 
begun to germinate, is in the four nucleate stage. 
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