362 



GENERAL MORPHOLOGY OF PLANTS 



spore (macrospore) is formed inside, which never escapes, but 

 develops the female prothallium or gamete plant 

 (gametophyte) , which in the Gymnosperms is known 

 as the endosperm. In this prothallium, egg cases 

 (archegonia) are formed near the micropyle, each 



Fig. 349- 



Section of female 

 cone of white pine, 

 showing young ovules 

 (macrosporangia) at 

 base of the ovuliferous 

 scales. 



Fig. 350. 



Scale of white pine with 

 he two ovules at base of 

 ovuliferous scale. 



Fig. 35i- 



Scale of white pine seen 

 from the outside, showing 

 the cover scale. 



containing a large egg which is surrounded by a regular layer 

 of cells, the wall of the venter, called 

 jacket cells, or a jacket. After fertiliza- 

 tion the embryo is developed within 

 the ovule. The ovule together with 

 the endosperm and embryo forms the 

 seed. The scales have become large 

 and hard. It requires about fifteen 

 months from the time of pollination 

 (during May) to the ripening of the 

 sp* seed (August of the following year). 

 Soon after the ripening of the seed, 

 the cone dries. As this takes place 

 the seed with a thin layer of the 

 scale, in the shape of a knife blade, 

 splits off from the scale. The pine 

 seed, therefore, is a " winged " seed. 

 530. Pollination and fertilization. At the time the pollen 



is scattered the small pistillate cones stand erect, with the scales 



..a" 



Fig. 352. 



Macrosporangium of pine 

 (ovule), int, integument; , 

 nucellus; m, macrospore; pc, 

 pollen chamber; pg, pollen 

 grain; an, axile row; fpl, 

 spongy tissue. (After Fer- 

 guson.) 



