144 THE NATURE AND VARIETIES OF 



In mosses, then, as in the Trematoda, the gemmation 

 must be held to occur in a germinal or rudimentary (proto- 

 morphic) stage, whereas in ferns, as in the Polypifera, it is 

 delayed till the formation of an axis, in which the general 

 organization reaches its culminating point, though without 

 the development of organs of fructification, which make 

 their appearance only subsequently in the prothallia — de- 

 rived from it, as the medusoids are from the zoophyte — 

 both being, as it were, supplementary structures, and having 

 for their main end to supply the deficient organs. In the 

 moss the parts of fructification are attached to the axis 

 more persistently, and with less intervention of floral enve- 

 lopes than in any other plants, while in the fern they are 

 not produced at all, till after the fall of the fern, spore, and 

 the development from it of their matrix by a subsequent 

 process of independent growth. However disguised by this 

 detachment and growth — the prothallium, as the ma.trijj of 

 the spermatic and germinal elements, must remain the real 

 homologue of the floral organ of a phenogamous plant, and 

 the illustration furnished by the floating flower of the 

 Valisneria comes in here even more appositely than in the 

 case of the Polypifera. 



It will be observed, however, that in thus indicating a 

 relation between ferns and mosses, similar to that subsist- 

 ing between the Polypifera and Trematoda, arguments of 

 analogy only have been made use of. No reference has 

 been made to transitional forms, such as those which furnish 

 so important a clue in the last mentioned case, for in fact 

 no such forms have yet been recognised among the Crypto- 

 gamia, though, as their existence is quite conceivable, their 

 discovery may possibly reward the labours of some future 

 botanist. A case could readily be imagined, for instance, 



of Keproduction in the ABimal and Vegetable Kingdoms, Annals of 

 Nat. Hist., 2d Ser., xx. pp. 241, 344, 439. 



