242 Mr. C. Jenner on the Development of the 



case the cellular frond which bears the archegonial cells, 

 whereas in the Selayinella the analogous cellular expansion is 

 developed witliin the spore-case. 



It thus became apparent to me at the very outset of my 

 investigations, that in considering the question of the entire 

 cycle of an individual life among these plants, we should never 

 lose sight of the fact, that there is no such identity among the 

 spores of the higher Cryptogams, as is supposed to exist among 

 the embryogenic seeds of Phanerogams ; and also, that we 

 should err as much in assuming the spore, at the period of its 

 vegetative development, to represent the earliest stage in this 

 cycle, as we should, were we to consider the seed as the first 

 stage of the existence of a Phanerogamous plant, overlooking 

 the origin and development of the embryo, its envelopes and its 

 albumen, and the special relation which these latter bear to the 

 parent plant. 



All plants above the lowest possess special cellular structures, 

 within which, as within the ovular envelopes, or in the sub- 

 stance of which, as in the pro-embryo of a Fern, there is pro- 

 duced an embryonal chamber or sac. In the intei'ior of this 

 cell the protoplasm or formative matter is concentrated, from 

 which is evolved the whole after- structure. Thus, in Mosses, in 

 Lycopodals, and in Ferns, as well as in Phanerogamous plants, 

 it is a single cell within which the subsequent development is 

 called forth through the influence of fecundation. This germ- 

 cell is in every case the commencement of the new individual 

 cycle of life. 



To enable me to trace, as carefully as I propose, the analogy 

 between the principal organs and stages of development of the 

 higher Cryptogamic plants and the Phanerogamic, I must ask 

 you to dissociate in your minds this germinal vesicle from the 

 structure within which it has its origin. These investing organs 

 are very varied in their form and texture. The most striking 

 difiFerences prevail between them in Gymnospermous plants and 

 Angiospermous plants, and also between them in the orders and 

 even genera of Angiosperms and the several orders of Cryp- 

 togams ; while, on the other hand, there is an approach to homo- 

 geneity in the form, structure, and early general development of 

 the germ-vesicle itself, so that unless we dissever, as it were, this 

 germ- vesicle from those heterogeneous environments (which have 

 only for their purpose the sustentation and preservation of the 

 germ-vesicle), we shall trammel our subject with unnecessary 

 difficulty and fail to attam that clear point of view that is so 

 desirable. 



There are thus then certain structures, so intimately asso- 



