These capsules have been traced by Sprengel and Bernhardi, from their first developement in the young suc culent frond. They appear, when young, mixed with fila inents, which at first these eminent naturalists imagined to he the male organs ; an opinion which the genuine candour of Sprengel speedily relinquished for that already stated, viz. that the impregnation is affected by the concentrated proper juice czitained in the ascending vessels of the fas ciculi. We have already stated, that we cannot consider this process of fecundation to be effected solely by these vessels ;---why should we attempt to limit, by imaginary analogie e operations of nature ? Bernard de Jussieu sir long ago Mem. de l' Acad. des Sciences, 1740) demon strated the male organs of the Marsillacex (a tribe pos sessing evident affinity with the ferns,) within their cap sules. Now, although such organs have not hitherto been detected within the capsules of ferns, there seems nothing really absurd in conceiving seeds to be formed within these capsules, and perfected by the absorption not -merely of the ascending sap from the vascular fasciculi of the stem and frond, but from veins returning the sap elaborated in the reticular substance of the expanded fronds. That the
sap thus returns ,,from the fronds is highly probable, from the green colour, of the saccharine mucilage, a super abundance of which, we have already observed, is annu ally deposited for the developement and nutrition of fu ture germs in the stem itself.
Plate CCLIV. Fig. 9. represents a pinnule of Athyrium thelypteris, as delineated by Schmidel, in order to shcw the elegant ramifications of the vascular fasciculi, in contact with which the groups of capsules appear, covered with their respective involucra. Fig. 10. a highly magnified view of one of these, with the yellow globular bodies, imagined by Bernhardi to be male organs. Fig. 11. a capsule wit': its ring, beginnning to burst and eject the seeds.
These figures, then, although representing the fruit of the Aspidiacee only, we shall refer to as types of the re spective fruit of the whole series of ferns.
The groups of capsules are termed sori, from crovs, to mtits. In many genera, these groups are covered with an involucrum, as represented in the Figure ; but in others they ;tie quite naked. This involucrum is evidently a pro duction of the cuticle, and, in its early state, is organised exactly in the same manner.