188 REPRESENTATION OF THE 



sporangia of the ferns reminding us of the contrast be- 

 tween the common Hydra among the Polypifera, with its 

 simple genital cysts, and the complex gonophores of other 

 species, developing free medusoids. 



The complexity of the genetic cycle of mosses is not in 

 the processes which precede, but in those which immediately 

 follow on impregnation, as was before shown at some length 

 in contrasting the phenomena of alternation in these two 

 groups. In fact there is almost as much difficulty in 

 pointing out, in the flowering plant or fern, any homologue 

 to the spore-case of the moss, as in demonstrating in the 

 latter any part corresponding to an ovule or a prothallium.* 



10. It would apppear, therefore, that the results of 

 the examination of the reproductive process in the Vege- 

 table Kingdom are quite in harmony with those before 

 drawn from a survey of the corresponding phenomena 

 among animals ; both leading to the conclusion that some- 

 thing which may stand for a representation of an alternation 



*" It may be thought that the suspensor of the embryo represents the 

 seta and theca ; but in the mosses and the foliaceous Hepaticse there is, 

 besides this, another form the confervoid protonema interposed before 

 the development of the leafy axis, so that one at least of these structures 

 must be wholly unrepresented in the higher species. In the Conifer 

 there is something analogous to the multiplication of spores in the theca 

 of the moss, for the primary " embryonal vesicle" originates four sus- 

 pensors, each with its proper embryo, all, however, normally aborting but 

 one (as in the case of the " Corpuscula" themselves), so that here, as iri 

 other plants, but a single embryo is eventually developed from the seed. 

 On the other hand, it may be observed, that in some species of Mar- 

 chantia among the Hepaticse there is a stalked receptacle of the organs 

 of fructification, which may admit of comparison with the floral organ of 

 the Phanerogamia, or the capsule spore and prothallium of ferns. The 

 peduncle in these cases has obviously very different homological relations 

 from those of Jungermannia, for though both, when in fruit, support the 

 spore-cases, that of Jungermannia is a much later formation, being 

 evolved from the archegonial corpuscule, while that of Marchantia pre- 

 cedes the archegonia, which are developed from the parenchymatous 

 mass of its summit. 



