. Botany of the living plant. Botany; Plants. FILICALES 509 * & ./- frcn is preceded by a sort of irregular fertilisation. The nu< letlfl | cell through a pore in the cell-wall into the next cell. I here it hues with the nucleus of the invaded cell (Fig. 403). Doubtless there is here a donblin| the chromosomes, as in normal fertilisation ; and such a cell, like a f. zygote, may serve to initiate the sporophytic bud. The proo styled pseudomixis to suggest a comparison with sexuality, while marking it^ distinctness from it. In other cases careful investigation has shown that a gametophyte
. Botany of the living plant. Botany; Plants. FILICALES 509 * & ./- frcn is preceded by a sort of irregular fertilisation. The nu< letlfl | cell through a pore in the cell-wall into the next cell. I here it hues with the nucleus of the invaded cell (Fig. 403). Doubtless there is here a donblin| the chromosomes, as in normal fertilisation ; and such a cell, like a f. zygote, may serve to initiate the sporophytic bud. The proo styled pseudomixis to suggest a comparison with sexuality, while marking it^ distinctness from it. In other cases careful investigation has shown that a gametophyte may be diploid. Transition from one generation to the other may then be re] while uniformity of chromosome-number is maintained throughout. Thi seen in Athyrium filix-foemina, var. clarissima, where the number is 90, approximately that for the normal sporophyte of that species. The same is the case for certain plants of Marsilia Drummondii, which are diploid throughout, with 32 as the number. It is probable that the converse is the case for Dryopteris pseudo-mas, var. cristata (Fig. 404), for the chromosome-number throughout was found to be variable, from 60 to 78, while in that species the normal number for the sporo- phyte is 144. Not only do such cases show that the usual chromosome-cycle may be departed from, but also that the external characters are not directly dependent upon the chromosome-number. The cycle of life of a Fern shows more clearly than that of any of the Vascular Plants hitherto described the antithesis of the two generations which constitute it. Each can grow, nourish itself, and even multiply independently of the other. It is true that the young sporophyte is nursed temporarily in the parent prothallus. But this is only a transient event and is soon over. A similar nursing period, with much greater adaptive detail that lends added efficiency, is seen in the Seed-Plants. The main difference between the Seed- Plant and the Fern lies in their spores. The for
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