EMBRYOGENESIS IN LEPTOSPOR ANGI ATE FERNS 



147 



phyllorhize is the foot, by which the phyllorhize is attached to the 

 prothallus. At the base of the phylle hes the residual meristematic 

 mass, corresponding to the shoot apex, from which the second 

 phyllorhize will be formed ; and there is always a residuum of this mass 

 available for the formation of further phyilorhizes. Chauveaud further 







Fig. 35. Embryogeny in leptosporangiate ferns 



A, Pteris serratula. First division of zygote, as seen in l.s. of the archegonium (a); 

 the smaller segment is towards the prothallus apex (ap); p, prothallus. B, C, 

 AdiaiUitm coiicinnum. B, Post-octant stage, as seen in a longitudinal median section 

 of the prothallus and archegonium; ap, direction of apex of prothallus; s, shoot 

 apex; /, first leaf; /, foot; i; first root. C, Older embryo, still enclosed in the pro- 

 thallus; lettering as before. D, Onoclea sensibilis. Fully formed embryo, with first 

 and second leaves, /^ and /j; sa, shoot apex. (A, B, x 250; C, x 135; after 

 Atkinson; D, x 48; after Campbell.) 



recognises that the base of the phylle has a shoot-like character and 

 this he designates as caule, the upper foliar portion being recognised as 

 feuille (leaf). This theory of construction in the ferns rests on the 

 following facts: (i) that in many ferns there is a very close correspon- 

 dence between the number of leaves and of roots, e.g. young plants of 

 Alsophila australis, Gymnogramme sidphurea, Ceratopteris thalictroides, 

 Scolopendrium vidgare, Polypodium vulgare, and others, may show four, 

 five or more perfect phyilorhizes; (ii) that the vascular tissues run from 



