Fig. 21. Embryogeny in Equisetiim 

 A, B, E. anense. Young and older embryo, in longitudinal section (after Sade- 

 beck) ; I-I, first wall of zygote, at right-angles to archegonial neck. C, E. maximum. 

 Germinating spores. D-J, E. debile. Development of embryo ; the first or basal 

 wall, b-b, may vary in position from horizontal to vertical and the embryo, which may 

 pass through an almost perfect octant stage, tends to become flattened; the shoot 

 apex, and perhaps the first root are of epibasal origin, the hypobasal cell giving rise 

 to the very large foot; s, shoot apex; r, root; Is, first whorl of leaves; /, foot; a, 

 archegonial neck. (D, x 240; E-J, x 270). (C-J, after Campbell). 



