OTHER FORMS OF ALTERNATION. 185 



phanerogamic plant the pollen, instead of being generated 

 in anthers, as distinct floral organs, were formed in cells 

 within the ovule, lying side by side with the embryo-sac 

 containing the germinal corpuscules. It is of course need- 

 less to say that no such arrangement is met with in any 

 plant ; but, at the same time, there is observable a great 

 variety in the mutual relations of the sexual organs. Their 

 location in distinct individuals, by what is termed a dioe- 

 cious arrangement, though common in animals, is rare 

 among plants. So is also that rather closer approximation, 

 known as monoecious, in which, though the stamens and 

 pistils are in distinct flowers or when these arise from dif- 

 ferent buds, may even be said to be in distinct phytoids 

 yet they always co-exist within the limits of the entire 

 plant, or as some would term it, the physiological indivi- 

 dual i.e., the product of the same original act of di- 

 genesis. But in plants it is by far most usual to have both 

 kinds of organs within the same floral envelopes ; while in 

 what are termed gynandrous flowers, the anthers and the 

 ovuliferous carpels are more or less fused together. We 

 have only to suppose the approximation carried a little 

 farther to have an arrangement comparable to that met 

 with in the prothallium of a fern. 



The comparative unimportance of this arrangement is 

 farther shown by its absence in the allied cryptogamic 

 orders of Rhizocarpese and Lycopodiaceae, in which the 

 general course of embryogeny so much resembles that of 

 ferns. In Rhizocarpeae the spore-case contains two kinds 

 of bodies, the larger answering in so far to the fern-spores, 

 that in germination they develope a prothallial layer con- 

 taining archegonia ; only, as already remarked, this is of 

 comparatively small size, and never protrudes beyond the 

 spore-coat. It has this farther peculiarity, more relevant 

 to our present subject, that it developes no antherozoids, 

 these corpuscules being the exclusive product of the smaller 



