With respect to duration, each frond is analogous to a single seta of a moss, it has definite limits, and is unlike the fronds of certain Hepaticae, which are capable of compound growth; or if this is the case in ferns, as it is in viviparous ferns, the new formation becomes separated from the frond, as a Phaenogamous gemma does.  This is a question of importance, as perhaps it may prove that all the foliaceous forms, except Lycopodium, Equisetum, and Chara, are frondose; the dorsal situation is in favour of this assumption, since in all the genuine frondose forms, the reproductive organs of both kinds originate immediately from the under surface, although they may protrude through the upper.

I here ask, is there not prima facie evidence that these organs have peculiar functions; a peculiar form, attended with peculiar changes, must have peculiar functions; and will any one show me in any single instance, like circumstances to the like extent, in any of those organs called hairs?  By the bye, ferns themselves may prove that however like these are to certain forms of hair, yet that their functions are different, because the glandular hairs of ferns do not undergo the same alterations, and are evidently nothing but hairs, probably secretory.

19th.—­In Ceterach the same thing occurs precisely, with this difference, that the capita of the ramenta are highly developed; and still more, that the terminations of each pinnula of the young frond, are mere scales without a terminal head.

So that almost all the scales of the under surface of the lobes of the mature frond, are mere scales.  The peculiar ramenta are to be looked for along the insertion of each pinna, and along the rachis, in which all have the peculiar structure.

At the time that these scales are commencing their development, the peculiar ones are at the age of mature perfection, so far as function goes.  No one can look at a young pinnula at this epoch and observe the evident capitation of each ramentum, the inflexion of its apex, so that the head is brought into contact with the frond, without suspecting that they have the same relation of cause to the appearance subsequently of the thecae or capsules.  It is curious that the colour of the scales is the same as that of the ramenta, in which the colour is developed from above downwards, a peculiarity as it appears to me.

The frond of Ceterach is very frondose-looking, it has stomata on its under surface, and the cells of the cuticle very sinuate.  There can be no doubt of the propriety of including the nature of these ramenta and scales in its generic character.

I can see nothing peculiar in the situation of the scales or ramenta to suggest the reason of the situation of the capsules.

In several cases, each pinna appears to have scales only which become barren lobes? the scales and ramenta have the same imbricate situation.  In this country it will be useless to expect more proofs.  But the four genera alluded to afford evidence enough, and sufficient to show that these ramenta are formed with reference to some important function, that their universality is incompatible with any functions of such minor degree as are attributed to them by those who represent them to be scales or hairs.