552 



LIFE-HISTORIES 



r _ r 



c Xa 



W I 



I 



^ ic 



rot.- 



Fig. STO. — Norway Spruce. Fertilization of egs-cell. -1, ripe egg-cell with 

 nucleus ion) and lower neck-cell (c/), V. B, same, later, the tip of a 

 poUcn-tubc (p) having entered the egg-cell and discharged into it the 

 male nucleus {sv) which approaches the female nucleus (ors). C, same, 

 later, the two nuclei ha-\-ing 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. E, 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. (?, same, after the middle 

 tier of cells has elongati-d to form a suspensor which has pushed the 

 lower tiers of cell into tiie prothallus (or endosperm) where the^- gi^'C 

 rise, by repeated cell-division, to an eml:)r3-o which is fed by the endo- 

 sperm. The nutritions materials left over in the endosperm when the 

 ovule has become a y(?ed constitut(^s the sei'd-foiKl w"hich supports the 

 \'oung phmtlet during germination. (Strasliurger.) 



spreading carpel, they come finally to the micropyle where ihe 

 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 ]iart of the male gametojih^'te ; while others, 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 



