INTRODUCTION. 13 
order, is so great that, to say that the plant belongs to a certain order, is 
at once to give the greater part of its description. This is the case also 
in the highest or most general groups. For instance, to say that a 
particular species is an Exogen, is at once to make known the structure 
of its stem, and the mode of its increase,—to express the important fact 
that it has two cotyledons or seed-leaves,—to render it most probable 
that the arrangement of the veins in its leaves is reticulated rather than 
parallel,—and to intimate that the parts of its flowers are likely to be 
arranged in fives or fours, rather than in threes, 
CONNEXION OF STRUCTURE AND PROPERTIES. 
7. There is a point of agreement among the plants brought together 
in Natural orders, which is of the greatest practical importance. This is 
that those which agree in structure almost invariably correspond in 
properties also. For instance, the whole of the Papaveracee or Poppy 
tribe possesses narcotic properties; all the Rannuculaces or Crowfoot 
tribe are acrid; whilst all the Malvacez: or Mallow tribe are destitute 
of unwholesome properties. Thus, when a plant is recognized as a 
member of a particular Natural order, an almost certain account may be 
given of its properties,—whether it is likely to be injurious or whole- 
some, to furnish valuable medicines or important articles of food. It 
must be remembered, however, that the peculiar properties of the plant 
do not pervade every portion of it; and that it may hence be possible to 
obtain wholesome nutriment, even from members of orders most distin- 
guished for their deleterious properties. Thus the Potato belongs to 
the order Solanez, which contains the Deadly nightshades, Henbane, 
and other poisonous plants, but the edible part of it, which is a deposi- 
tion of starch for an express purpose, is free or nearly so, from the 
narcotic properties which exist in the stems and leaves. Indeed as a 
general rule, such depositions of starch may supply wholesome food in 
any order, more especially if care be taken to free them from any juices _ 
they may contain: thus the Cassava which furnishes one of the most 
important articles of food to the inhabitants of many tropical countries, 
is obtained from a plant of the order Euphorbiacee or spurge tribe, 
which is distinguished for its very acrid qualities : and these are restricted 
to the juice expressed from the meal after it has been ground. 
USE OF THE LINNA:AN SYSTEM. 
8. The Linnzan system, however, is not without its advantages, for 
particular purposes. To a person commencing by himself the study of — 
Systematic Botany, desirous of making himself acquainted with thenames. __ 
and characters of the plants he may meet with in his walks, and not _ 
ambitious of extending his studies to the higher parts of the science, the : r 
