EMBRYOLOGY 



393 



FIG. 214. 



Embryo of Equisetum. I. -IV., Equisetum arvense, L. I. and II., the same embryo 

 in different positions : in I. the median wall is visible, in II. the transverse wall. X3oo. 

 1 1 1. -IV., a more advanced embryo showing development of the stem and leaf-sheath. 

 X250. V., an embryo still further developed, but not dissected free from the prothallus, 

 and showing the orientation relatively to the archegonium. st = the stem apex ; z> = the 

 first leaf-sheath; w = the root. Xg8. VI. and VII., Equisetum palustre, L. VI. = 

 young embryo still in the archegonium, stem and foot are visible. X^oo, VII. =an 

 embryo further advanced, and dissected free, and orientated 90 as compared with VI. 

 The root (/) and stem (st) are visible. X 300. b basal wall ; T= transverse wall ; m = 

 median wall; t' = epibasal and //=hypobasal region; e/ = the first leaf-sheath. (After 

 Sadebeck, in Engler and Prantl. Nat. PJlanzenfam.} 



