38 
RUDIMENTS OF THE NATURAL SYSTEM OF BOTANY. 
Partly from such reasons, and perhaps, likewise, from some striking singularity 
of structure which the most enlightened and piercing eye cannot exactly fathom, 
the precise mode of their enlargement is by no means well authenticated. Our 
analysis of the commonly received theory will be mainly restricted to the arbores- 
cent forms, because, in the smaller herbaceous species, it is next to impossible to 
arrive at any satisfactory conclusions, on account of their short duration and very 
rapid growth. 
Palms, and the species of Pandanus, or screw-pine — many of the former of 
which, and a few of the latter, may be seen in those gardens that contain exten- 
sive hothouses — constitute the most gigantic and simple forms of Endogenm, and 
their composition should, in consequence, be most sedulously studied. It has been 
affirmed that they consist, primarily, of the same constituents as Exogens, and 
that their diversity of form is assumed at the close of the first year's extension. 
However this may be, an old stem exposes to view a mass of cellular tissue, in 
which a vast quantity of longitudinal bundles of fibres is imbedded. "We have 
before us a piece of palm-wood, wherein this structure is very plainly perceptible. 
It can be reft longitudinally into as many strips as there are fibres ; yet these last 
are almost as hard as metallic substances, and cannot be cut with a knife. 
But some species of palms, instead of having their fibres disposed in a direc- 
tion parallel to the elongation of the stem, display, on being severed, such an 
extraordinary intermixture of them, with such various tendencies in each, that it 
is with extreme labour their course can be traced. We cannot but suppose these 
departures from the ordinary route. The best-established form is certainly that 
in which they take a direct downward line, diverging only when opposed by 
unnatural obstacles. 
Pandanacew must be excepted from the above assumption. Their vessels, 
striking into the stem from the bases of the leaves, proceed down its centre to the 
place where it becomes narrower, when they shoot outwards, emerge through the 
cuticle, inclining towards the earth, and continuing to grow in this position till 
they penetrate the ground, and fulfil the offices of roots. There is something 
apparently quite unique in the habits of this group of Endogens, though, in 
reality, they do not depart from the customary conformation ; serving to explain 
much of what seems extremely dubious respecting the development of the plants 
composing the sub-class. 
A slight survey of our specimens of the Pandanus, will convince the reflecting 
observer that the leaves are the great laboratories of all solid accretions, and the 
sources from whence they issue. Passing from thence, the ligneous fibrils descend 
through the cellular substance, where, acquiring a motion towards the surface 
as they advance, probably through the force of the central rising fluids, they burst 
from their exterior covering, obtain a new epidermis by exposure to the air, and 
after the lapse of several years have all the appearance of separate stems. Could 
we see one of these plants for the first time, with a circle of such extraneous 
