xxvi E PREFACE. | 
But as this is the first work, arranged according to the natural system, 3 
intended for the use of Indian botanists, whose portable libraries can ad- - 
mit of but few publications on the subject, we shall take the liberty of 
concluding this rather lengthened preface by the following short intro- 
duction to the principles of the system and the classification we have 
adopted, written by Mr Arnott originally for the seventh edition of the 
Encyclopedia Britannica, and published in the fifth volume (p. 92) of 
. that work. 
k When different seeds taken from the same plant are made to germi- 
nate, we have individuals not entirely agreeing in the shape of the leaves. 
or the height of the stem; from which we may infer that characters de- 
rived from these are of the least importance; and consequently, when 
we describe species, we must use such with great caution. . But when we 
rise a step higher, and group species into genera, we find so great a va- 
riety in both the stem and leaves, that we are forced to look for charac- 
ters elsewhere, and thus resort to the different parts of the flower; and 
all genera are therefore founded on a consideration of these. When, 
however, we come to examine a genus by itself, we shall find that per- 
haps none of these parts are sufficiently constant, some species differing 
from others in the number or shape of the sepals, or petals, or stamens, 
or pistilla, so that we are obliged to eall into action not any particular 
one, but a combination of the whole. While doing this, it cannot eseape 
our notice that the more external portions, as the calyx, exhibiting: 
more of the foliaceous origin, are less constant than the petals ; and these 
again less so than the stamens; but the stamens and pistils having least 
of the structure of the original leaf, are the most uniform : and henee 
Linnzus, influenced principally however by these being the true sexual 
organs, adopted the stamina and pistils as the basis of his system, Now 
in many natural genera, plants differ from one another only.specifically 
although there happen to be a difference in the number of parts of the 
reproductive organs; so that number, not being at all times sufficient to 
constitute a genus, can still less be relied on for a higher division. The 
structure must thus be considered, and this we not only find common to 
the species of a genus, and even often to different genera so allied in as- 
pect, that at first we might consider them all as one great genus; and 
such great genus being in faet an order, we are led, while defining it, to 
place considerable dependence on the strueture of the anthers, but more 
especially on the fruit, the ultimate metamorphosis of the primary leaf. 
But on comparing together two or more orders otherwise very closely 
allied, we often perceive very different structures of the fruit, so that, in 
search of something more fixed, we are compelled to dip still deeper in- 
to the economy of the plant and examine the seed. Here, indeed, we 
