1840.] 



Wight's Illustrations of Indian Botany. 



379 



first instance, surmounted in acquiring a knowledge of its principles. 

 These, in the present instance, are not by any means so great as they have 

 been represented ; for, as Jussieu well observes, whatever trouble is ex- 

 perienced in remembering- or applying the characters of natural orders, 

 is more than compensated by the facility of determining genera, the 

 characters of which are simple in proportion as those of orders are diffi- 

 cult. The reverse takes place in arbitrary arrangements, where the 

 distinction of classes and sections are simple and easy to remember, 

 while those of the genera are in proportion numerous and complicated. 

 On this question, therefore, as there can scarcely be two opinions, it now 

 only remains for me very briefly to explain the principles of the ar- 

 rangement or distribution of the orders, adopted both in this work and 

 in our Prodromus. 



" The arrangement followed is very nearly that of Jussieu, as modified 

 by DeCandolle, and adopted in his Systemaand Prodromus. According 

 to this system, all plants are first distributed under two principal classes, 

 Cellular and Vascular, the former comprehending all the plants desti- 

 tute of spiral vessels and of Cotyledons — Cellulares; the latter, in- 

 cluding all the flowering plants which are furnished with both these 

 organs — Vasculaues. The vascular plants, of which only we have as 

 yet treated, are again divided into two classes — Dicotyledons or Exo- 

 genous plants, and Monocotyledons or Endogenous plants. To the 

 former, all trees and shrubs which increase in thickness from the centre 

 towards the circumference by a succession of concentric layers of wood, 

 belong, as well as neaily all those herbaceous annuals, the leaves of 

 which have iet...ulated or anastomosing vessels. To the latter the 

 various kinds of grasses, Lilies, Orchidice, Palms, Plantains, &c. be- 

 long; the vessels of the leaves of which pass either in straight lines 

 from the base to ilie apex, or from the midril to the margin, and the 

 leaves are sheathing, in place of being attached by a joint to the stem. 

 These distinctions are not without exceptions; but the exceptions are 

 so few as scarcely, in practice, to affect the value of the rule. These 

 primary divisions, though thus based on the most obscure and ditlicult 

 portions of vegetation to investigate, the minute structure of the seed 

 and organization of the stem, are, in fact, the easiest, generally speaking, 

 of determination ; the simple circumstance of a plant having a flower, 

 proving that it has spiral vessels, while the practised eye of a botanist 

 can, almost invariably, tell at a glance, by merely inspecting the distri- 

 bution of the vessels of leaves and structure of the stem, whether the 

 seed is mono : or dicotyledonous. Having, by this summary process, 

 decided to which division of the system a plant belongs, we proceed 



