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92 PATTERSON v. M'CAUSLAND.
tinct as the tree grows older; and that the fibres of the wood of
some are very singularly disposed, appearing to have been col-
lected into bundles; or to have undergone some peculiar inflexions
as the tree advanced in age. We know that, here, roses do not
bloom in January, that apples do not ripen so early as April, nor
cherries so late as October; and we also know, that some forest
trees bring their fruit to maturity annually, and others only bien-
nially; that some trees are of the moncecia class, having the male
and female organs on the same tree, and that others are of different
sexes, or of the diaecia class, having the males and females in dis-
tinct trees. These peculiarities, and the periodical fructification of
trees being known, as in the case of the known terms of the incu-
bation and gestation of animals, the law respects and confidently
relies upon such a known regular course of nature. But no series
of observations, by botanists or cultivators, have as yet demon-
strated that any portion of the wood of a tree, as visible to the
naked eye on dissection, was, like its fruit, the result of successive
periodical formations, known to have been made within certain
spaces of time; nor have philosophers, with the aid of chemistry
or the microscope, been as yet able, in this and a multitude of
other particulars, to detect the latent operations of the vital prin-
ciple in vegetation; leaving all questions as to its gradual or
periodical progress, still covered up in the most impenetrable
obscurity, (a)
(a) Thompson's Chem. b. 4, c. 3; 11 Westm. Revw. art. 8, p. 97; Vegetable Phy-
siology and Arboriculture; Roget Anim. and Veget. Physi. pt. 1, c. 1, s. 2 and 3,
pt. 2, c. 1.
'We know the substances received by plants, and those which they reject; we
determine by analysis the nature and the composition of the products which they
form; but this is the utmost extent of our knowledge. All that passes within the
plant is still a mystery, and belongs to the laws of vitality, which modify by their
action those physical laws that are known to us.'—Chapters Chemistry applied to
Agriculture, c. 5, art. 6.
* Plants may be considered as a set of machines by which the common elements
of nature are worked up into such a form as to be fit for the sustenance of animal
life. We have already examined the structure of this machine; we will now direct
our attention to the way in which it operates. In this department of the science,
the difficulties which the philosopher has to overcome are of a very different cha-
racter from those which may have embarrassed him in merely determining the
organization of the plant In the latter case, good microscopes, manual dexterity in
preparing the parts for examination, and sufficient patience for his task, are sure to
bring the observer to conclusions, the general truth of which is often susceptible
of exact demonstration; bat when we come to consider the causes of vital phe-
nomena, and the manner in which they are brought about, we have obstacles
of quite another kind to overcome. There is not a function of vegetable life
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