324 



BOTANY 



B 



em 



FIG. 286. Pinus Virginiana. A, sec- 

 tion of ovule, showing the gameto- 

 phyte, a, with two archegonia, ar; 

 p, pollen grains sending pollen-tube 

 through the tissue of the ovule. JB, 

 P. edulis, section of ripe seed (X 2) ; 

 g, gametophyte ("endosperm"), en- 

 closing the embryo sporophyte. 



ened membrane. It always re- 

 mains permanently within the 

 sporangium. 



Ovule. Within the macrospo- 

 rangium (Fig. 286), known in the 

 Spermatophytes as the " Ovule," 

 the single macrospore gives rise to 

 the female gametophyte. The 

 sporangium is invested by one or 

 two envelopes, or integuments, 

 which are characteristic of the 

 ovule in all typical Spermato- 

 phytes. 



The Gametophyte 



Male Gametophyte. The male 

 gametophyte is always extremely 

 reduced. There are from one to 

 three sterile cells, and a small 

 antheridial cell (Fig. 287, C, D) 

 within which is a nucleus, which usually divides later into two, the 

 male or generative nuclei. These correspond to the sperm-nuclei of 



FIG. 287. Cryptomeria Japonica. A, branch with male flowers, 5, slightly 

 enlarged. B, scale with pollen-sacs (microsporangia), I, from within; II, from 

 without (x4). C, pollen-spore (x600); an, antheridial cell. D, germinating 

 pollen-spore. E, female flower (X2). F, a scale with three ovules, o, more 

 enlarged. 



