552 
Fia. 
LIFE-HISTORIES 
B 
379.—Norway Spruce. Fertilization of egg-cell. A, ripe egg-cell with 
nucleus (on) and lower neck-cell (cl), 72. 8B, same, later, the tip of a 
pollen-tube (p) having entered the egg-cell and discharged into it the 
male nucleus (sn) which approaches the female nucleus (on). C, same, 
later, the two nuclei having become fused into one, which soon divides 
into four nuclei that move to the lower end of the egg-cell. D, lower 
end of the egg-cell showing two of the four nuclei which have moved 
into it. EH, same after division of the four nuclei into eight. F, same 
after further division has produced four tiers of nuclei, all but the 
uppermost four being enclosed in cell-walls. G, same, after the middle 
tier of cells has elongated to form a suspensor which has pushed the 
lower tiers of cell into the prothallus (or endosperm) where they give 
rise, by repeated cell-division, to an embryo which is fed by the endo- 
sperm. The nutritious materials left over in the endosperm when the 
ovule has become a seed constitutes the seed-food which supports the 
young plantlet during germination. (Strasburger.) 
spreading carpel, they come finally to the micropyle where the 
integument is often prolonged in such a way as to lead them directly 
to the tip of the nucellus. Here they germinate by forming a few 
cells, some of which, remaining within the spore, represent the vege- 
tative part of the male gametophyte; while othe*s, the male gametes, 
form a hypha-like tube which penetrates the soft tissue of the 
nucellus and feeds upon it like a fungus. Meanwhile the macrospore 
