428 
STRUCTURE AND LIFE HISTORIES 
contents of the nucellar tissue, thus facilitating the 
passage of the delicate tube. The dissolved con- 
tents nourish the growing tube, which at first serves 
as a haustorium to absorb the 
nourishment. Thus the male (as 
well as the female) gametophyte, 
lives as a parasite upon the tissue 
of the sporophyte. 
Soon after the pollen-tube has 
begun to form, the tube-nucleus 
moves down toward the tip, 
where it remains, presiding over 
the subsequent growth of the tube 
(Fig. 318). At about this time, 
also, the antheridial mother-cell 
divides, forming a wall-cell 1 and 
a generative cell. In this condi- 
tion the first winter is passed. 
After pollination the carpellate 
scales, by growth, are brought 
close together, and secrete a very 
FIG. 318. White pine 
(Pinus strobus). Germi- sticky, resinous substance, all of 
r&T B StSiS; whi <* very completely excludes 
g.c, generative cell; t.n, any water from between the scales. 
tube-nucleus. X about _.. , , . 
236. (After Margaret C. The cone then increases greatly in 
Ferguson.) 
s j ze (pj g> 
381. Fertilization. Early in the following spring (May- 
June), the generative cell, after passing into the pollen- 
tube, divides to form two sperm-cells, and the pollen-tube 
continues its growth toward the archegonia. By this 
time (June) the egg lies mature within, and completely 
1 Also commonly called "stalk-cell." 
