244 Mr. C. Jenner on the Development of the 



of the prothallus of the Fern, are, to speak briefly, homologous 

 and analogous organs. 



I now proceed to my particular purpose, which is to trace in 

 a general manner the cycle of development of a Moss, a Fern, a 

 Phanerogamous plant, and to trace in outline a few analogies 

 between their more important organs, which, if diverse in ap- 

 pearance and without any very apparent relation, have at least 

 common purposes. Nature is so infinitely varied in her forms 

 of manifestation, and she is so rich in her adaptation of means, 

 yet withal has such a clear and palpable unity of purpose, that 

 on the one hand we need not be surprised at apparent discre- 

 pancies, and on the other we need never doubt one common 

 identity. 



In the Table (p. 246) I have separated the investing organs 

 from the germinal body, and have shown the relation which I 

 hold the various organs of the plants under review have to each 

 other, and also distinguished the stage of development in each 

 order at which the resting condition is attained ; this condition 

 being in every case precursory of detachment from the parent 

 plant. The investing organs may be divided into general and 

 special ; the general investing organ being the ovarium in Angio- 

 spermous Phanerogams, the theca in Filices, and the arche- 

 gonium (in its ripened condition the sporangium) in Musci. 

 The special investing organs are those which immediately en- 

 viron the germinal vesicle ; these are, in the Phanerogamia the 

 coats of the ovule, in Filices the pro-embryo, and in Musci the 

 sporular integument which enfolds the nucleal germ, and which 

 finally constitutes the testa of the Moss-spore. The unimpreg- 

 nated germinal vesicle of the Phanerogamia finds its homologue 

 in the archegonial cell of the pro-embryo of the Fern, and in 

 the embryonal cell within the archegonium of a Moss. The 

 maturation of this cell is only preparative to the fecundative act, 

 or the fertilizing process, whatever that may be, which takes 

 place, in one or other manner not yet determined, in all plants 

 at this stage of progress. The impregnating influence or matter 

 being imparted to this vesicle, embryonal development ensues, 

 and always in the same general manner, varied only by the special 

 varying circumstances of each particular case. The fertilized 

 cell stands on the verge of the active development of an inde- 

 pendent vitality. In Ferns the resting stage is passed before 

 impregnation has taken place. The course of growth after im- 

 pregnation is continuous. The germinal body, by a succession 

 of transverse divisions, obtains the condition of a septate cellular 

 process, longitudinal and radial divisions follow, and a structure 

 is formed which developes an ascending and descending axis, in 



