Fig. 36. Embryogeny in heterosporous ferns 

 A, PUulaiia globiilifera. Archegoniuni in longitudinal median section containing 

 recently fertilised ovum; the archegoniuni (a) is shown in what is probably its 

 natural orientation. B-D, Marsilea vestita. Stages in the development of the em- 

 bryo, showing the differentiation of the shoot (,v), leaf (/), root (/•), and foot (/) 

 regions; p, prothallus. E, Pilnlaria globiilifera. Fully developed embryo in l.s., 

 still attached to the prothallus and megaspore {in), and enclosed in the calyptra 

 {cal)\ vs, vascular strand; other lettering as before (semi-diagrammatic). F-J, 

 A:olla filiciiloides. F, Young embryo as seen in l.s. of archegonium; the first 

 partition wall, I-I, is obliquely vertical. G, H, Young embryos in l.s. in which the 

 first wall is transverse to the archegonial axis: in H, the epibasal segment is forming 

 the apices of the shoot and first leaf; the first root initial can be seen in one of the 

 hypobasal quadrants, as in homosporous leptosporangiate ferns. J, Well-developed 

 embryo in l.s., after it has broken through the prothallus; lettering as before (all 

 after Campbell). (A, x 300; B, C, x 525; D, x 260; E, x 75; F-H, x 350; 



J, X 100.) 



