IV.] CRYPTOGAMS, 343 



essential organs, and our imperfect acquaintance with many 

 details of their structure and function, it is practically the 

 best plan to leave them to the last in a course of Elemen- 

 tary Botany like the present. Space compels me to be 

 brief in describing Cryptogams ; and those who desire to 

 extend their acquaintance with them I must refer to special 

 works which treat of them in detail. A few of these are 

 noticed in the list of works on Indian Botany given in the 

 Appendix. 



The development of the embryo in Flowering Plants 

 we have seen depends upon and immediately follows the 

 mingling by diffusion of the contents of two distinct cells 

 belonging to organs conspicuously contrasted morphologic- 

 ally — the pollen-grain shed by the stamens and the embryo- 

 sac of an ovule, — which organs may or may not be borne 

 upon the same axis. The plants which we have now to 

 consider, with the exception of certain groups of simplest 

 structure, generally present the same phenomenon of sexu- 

 ality, manifest in the mingling together, partially or wholly, 

 of the contents of distinct cells, which cells, however, or the 

 organs to which they belong, may or may not present any 

 external or morphological contrast. 



The immediate product of this mingling of the sexual 

 elements in Cryptogams varies very greatly in the different 

 groups, but it is never an embryo, with rudimentary 

 differentiation of organs, contained in a seed derived 

 from the tissues of the parent plant. 



One remarkable general difference between Phanero- 

 gamous and Cryptogamous plants consists in the pro- 

 minence in the latter of a more or less marked alternation, 

 in the cycle of development, of two distinct periods or 

 generations variously associated with methods of sexual 

 reproduction, and of asexual multiplication by means of 



