322 



BOTANY OF THE LIVING PLANT 



spermatozoids. As both types of spore germinate together , fertilisation 

 is readily carried out. 



After fertilisation the zygote secretes a protective wall, and elongating 

 in the axis of the archegonium, segments repeatedly (VI. -VIII.) to 

 form a suspensor (s) which, as in the Gymnosperms, thrusts the embryo 

 down deep into the prothallus (IV.). The distal cell soon enlarges, 

 and divides. It gives rise centrally to the apex of the stem (sf), with 



FIG. 265. 



Embryology of Selaginella denticulata, after Bruchmann. I.-III. ( x 12$) show 

 germination of megaspore. IV. vertical section of megaspore showing prothallus, 

 archegonia, and embryo (em) with suspensor (sus) ( x 50) . V. = a mature archegonium. 

 VI.-IX.=stages of developing embryo. X.= spermatozoids of S. cuspidata, after 

 Belajeff. ( x 250.) 



cotyledons right and left (c, c). Meanwhile unequal growth turns it 

 to one side, and the convex side enlarges into the suctorial " foot " 

 (IX. f). Lastly, the first root (wt) is initiated by periclinal divisions close 

 to the attachment of the suspensor, and on the same side of the embryo 

 (Fig. 265 bis, A, B). All the parts of the young embryo have thus been 

 produced, while the apex of the axis occupies the distal position from 

 the very first in the curved embryo. As the axis and root grow 

 they protrude from the ruptured spore, the root turning downwards, 

 and the elongating hypocotyl turning upwards (Fig. 265, II. III.). 

 The cotyledons already bear ligules (/, Fig. 265 bis). The further 

 development is merely a matter of continued growth and branching. 



