GROUP IV. — PHANEliOGAMlA : GYMNOSPERMJC. 



475 



Ephedra), there is a two-sided apical cell in the growing- point at 

 its first development. 



The cotyledons vary in number : one, in Ceratozamia, and some- 

 times in other Cycadaceae ; two, in the Cycadaceae generally, in 



the CupressineaB 

 generally, in some 

 Araucarias, in the 

 Taxoideae, and in 

 the Gnetaceae ; in 

 the Cupressineae 

 sometimes 3-5 ; in 

 the TaxodineaB 4-9 ; 

 in the Abietineae 

 5-15. The cotyle- 

 dons are generally 

 epigean : they are 

 hypogean in the Cy- 

 cadaceae, as also in 

 Araucaria (sect. 

 Colymbea) and in 

 Ginkgo among the 

 Coniferae: in the 

 Cycadaceae, and in 

 Ginkgo, the two hy- 

 pogean cotyledons 

 are closely coherent 

 at the apex, whereas 

 in these Araucarias 

 the cotyledons are 

 free. 



The growing- 

 point of the root is 

 in all cases differen- 

 tiated endogenously, 

 at some distance 

 from the posterior 

 end of the embryo. 



Thb Gametophyte. 

 — As the Gymno- 

 spenns are hetero- 

 sporous, the sexual 



Fio. 300.— Germinating seeds of Pmu« Pinea : I first 

 itoge, in longitudinal section : II second stage, with pro- 

 truding radicle ; A external view ; B view after removal of 

 half the seed-coat ; C longitudinal section, without seed- 

 coat; IJ transverse section, without seed-coat; III ger- 

 mination is here completed, the cotyledons having expanded, 

 and the hypocotyl elongated : a seed-coat; e endosperm ; lo 

 radicle; c cotyledons; y micropyle; r retl membrane (re- 

 mains of nucellus) ; x the embryo-sac. 



