Both lixmpfer and Daubenton have remarked, that the Phanir, or date-palm, and others of this series, require se veral years before they acquire their utmost diameter ; and that previous to this period, their stems do not begin to elongate, nor do their fronds acquire their perfect form and size. Now, in all these circumstances, they greatly resemble ferns. We know it has been frequently alleged, that certain species of ferns are stemless; an opinion coun tenanced by Sprengel, who observes, that ce in this case the fronds issue from the tuber or root ;" but having closely examined this supposed root, in the Davallia Canariensis, Polypodium aureunz, and other species asserted to be stem less, we found that they possessed the structure and all other properties of procumbent stems, detaching at inter vals proper fibrous roots, and diverging branches, and like the arborescent species, producing fronds from the nume rous buds at the extremity. Whether certain species, however, are altogether destitute of stems, it is impossible to determine with certainty; but such a circumstance is very improbable, and it is far more likely that such as are thus figured by Plumier and others, are plants in the se cond period of their growth, whose elongation had yet commenced. It is certain, however, that the smallest of our native species possess real, though very short stems.
These prostrate species form a singular contrast with those of the upright arborescent ferns. The Cyathea arbo rea, C. aspera, and other erect species, rival in magnifi cbnce the most lofty of the palms; yet, in the economy of their reproduction, these humble species certainly surpass them, being much more prolific in buds.
When the stems of these plants have attained their ut most diameter, they may be said to have arrived at puberty. The third period of their growth commences. The stem now gradually elongates, but except where it ramifies, in variably in a direction parrellel with the axis of the great vascular fasciculi ; and Sprengel is incorrect in.supposing the buds of the tuberous stern to be involute or circinate, like those of the fronds which germinate from it. These, in fact, consist of a round tuberous substance, of the same structure from the beginning as the maternal stem, exten ding longitudinally only.
The ridiculous fable of the old compilers of herbals, concerning the Baromez or Tartarian sheep, was long ago shewn by Linnxus to have originated from the singular ap pearance of the tuber of a species of fern (4spidium Ba romez,\Arilld. Sp. 10) covered with the brown woolly scales, common to many of these plants. It is certain, how ever, that the numerous ramifications of the prostrate stems, must necessarily prevent the growth of neighbouring plants, although they do not actually devour them like this chimerical sheep of the Tartars.
From the extreme slowness with which both ferns and palms arrive at an adult state, may we not presume that both partake of that longevity which it is well known palms possess, individuals of which are known to have existed above a century ? With respect to ferns, indeed, few of which are necessary to the wants of mankind, no observa tions, as to this circumstance, are recorded.
In tracing the organization of the stem of these plants, the, accuracy of Malpighi is again manifested ; for, to this excellent observer, we owe the first notice of their general structure. In a figure of a horizontal section of the stem of a fern, he exhibits the distinct fasciculi of spiral vessels, surrounded with cellular matter, "Disperses," he ob serves, " fibrosis fasciculis, et spiralibus fistulis compagina tur, ambientibus hinc inde, utriculorum seriebus." Of modern naturalists, Sprengel has given by far the best view of the structure of the stem of these plants, ac companied with figures highly magnified, of the central fasciculi of Malpighi. But however valuable an analysis of these parts be when thus exhibited, we have preferred an illustration of the general structure of the stem itself, as it appears when attentively examined by the naked eye, as affording a more correct outline, not only of the general structure, but of the relation the several parts of the stem bear to each other. Sometimes, indeed, it would seem, that confusion is produced by too high a magnifying pow er; and the subject intended to be represented, is rather obscured than clearly delineated, a circumstance which seems well illustrated by the highly magnified view given by Desfontaines, of a transverse section of the stem of a fern, in an excellent Memoir on the organization of monocoty ledonous plants.* In order to have the view of the parts as distinct as possible, it is necessary to cut the stem across, at a distance from the lateral buds.
Plate CCL1V. Fig. 7. represents a transverse section of the creeping stem of Asp/di= filix mas ; and Fig. 8. a longitudinal section of that of Davallia canariensis. In tracing the origin of the buds of these plants, it is clear that they originate from the cellular substance of the centre swelling, and in a manner forcing the vascular fas ciculi to accompany them in a lateral direction.
Fig. 7. a, The exterior cellular substance, part of which, in the stems of the great arborescent species, is externally converted into a substance of the density of horn, which is sometimes furnished with spines, but is, for the most part, in young plants, covered with woolly scales, each of which is furnished with a central fasciculus, probably vascular, issuing from a pore in the surface of the stem. These scales serve partly the purpose of hark, in protecting the young shoots, and evidently prevent the evaporation of the fluid part of the sweet juice which every where envelopes the germs of the future fronds and stems, which, in our northern climate, remain dormant du ring winter. The central cellular matter in ferns (Fig. 7. b) is not converted into wood, as in dicotyledonous trees, but remains soft and spongy, in the stipites at least, till finally absorbed during the ripening of the fruit. This substance abounds with a similar saccharine juice, often accompanied with an unpleasant astringency. The stem and the branch es of these plants are entirely cylindrical, unless acciden tally checked in their growth by removaSinto an unsuita ble soil, whereas the stem and branches of dicotyledonous trees are invariably conical, tapering towards the extremity.