66 SURVEY OF THE REPRODUCTIVE PROCESS 



Corpusculiim (arcliegonium) — imperforate ; 



Rliizocarps have also three germ-envelopes ; 



Spore-coats — pervious by the micropyle ; 



Prothallium ) . i .i ^ c ^\ i ±j. 



.1 • > pervious bv the canal oi the latter. 



Arcliegonium J 



In Ferns, from the spore being merely a provisional 

 structure, and from the prothallium being exposed, and not 

 enclosing, but only supporting the archegonium, the latter 

 is the only germ-envelope, and its canal the only passage of 

 access. 



In mosses, as has been shown, there is no body corres- 

 ponding to the spore of the ferns ; both it and the deriva- 

 tive prothallium, which in that group had already ceased to 

 be germ-envelopes, have now no longer any existence, the 

 archegonia being attached directly to the leafy axis of the 

 plant. 



§ 11. The general conclusion to be drawn from the fore- 

 going survey of the leading modifications of the reproduc- 

 tive process in plants, appears to be that the difference be- 

 tween the higher and lower species consists mainly in the 

 constructive energy of the former being as it were concen- 

 trated on that embryogenetic development, whereby a higher 

 degTee of organization is attained in the typical or ortho- 

 morphic condition ; the other two stages in the cycle of 

 propagation being represented only by the maturation of 

 the floral organs, and the formation of the cellular mass 

 which is the earliest condition of the embryo. The latter 

 process, though really the beginning of a new cycle, is so 

 blended with the concluding or gamomorphic stage of the 

 preceding, and both are so merged in the following ortho- 

 morphic phase of development, that their individuality is 

 quite lost, and they appear as mere subsidiary processes, 

 affecting only certain organs of the typical plant, Avhose 

 term of life is popularly supposed to commence from the 



