INTRODUCTION TO CKYPTOGAMIC BOTANY. 47 



tiguous cells. There is not, however, I think, sufficient to justify 

 us in considering the large spore of the Club -moss as homo- 

 logous with the embryo cell of Phsenogams, allowing as much 

 weight as possible to the facts. These large and small spores 

 are identical in origin, notwithstanding their difference of size. 

 Both, therefore, are homologues of pollen grains, but we have 

 no example of a pollen grain producing an embryo in its pro- 

 toplasm, though the cells of anthers, like other cells, may be 

 capable of development into buds. The embryo-sac, then, in the 

 Conifer, after many months is slowly filled with endosperm ; 

 cavities are formed at the apex, in addition to the large 

 central cavity ; particular cells in these little cavities or 

 corj)uscles divide, giving rise to a bundle of threads, and 

 after impregnation, the tips of these threads produce the 

 embryos, with the radicle pointing to the aperture of the 

 nucleus. Now, if the progress of the spore of the Club-moss be 

 followed, even allowing that it is the homologue of the embryo- 

 cell, the disc ought to be the homologue of the endosperm ; but 

 then if it were so, the whole leafy plant of a Moss or Liverwort, 

 which is clearly homologous with the disc of the Club-moss 

 spore, must be equally the homologue of the endosperm, which 

 is so clearly absurd, that at once all notion of homology ceases. 

 Allomng then the disc to be analogous to endosperm, the 

 archegonia are analogous to the cavities or corpuscles at the 

 upper part of the endosperm of Conifers.* The central cell 

 of the group, of which in the early stage the archegonia consist, 

 is analogous with the cavities of the corpiiscles. A cell is 

 similarly formed from its protoplasm, but then the develop- 

 ment of this is quite different. Up to a certain point there 

 has been considerable resemblance, but now, with strong 

 analogy, there is essential difference. 



34. In the Club-moss, a single cell at the base of the arche- 

 gonium divides ; a process is formed upwards, analogous only 



* It is sometimes said that these bodies in Conifers are without ex- 

 ample in other orders, but they are, possibly, only modifications of the 

 suspensors, as in Scrophidaria, from the swollen end of which the em- 

 bryo finally grows. 



