INTRODUCTION. 1] 
of burning will decide the question. The smell of a burnt 
bone, coralline, or other animal substance, is so peculiar, 
that it can never be mistaken, nor dove any known vegeta- 
ble give out the same odour.” 
27. A remarkable property of aon though not a 
means of diagnosis between them and animals, is their great 
tenacity of life ;—the length of time during which they can 
preserve the vital principle, as exemplified in seeds, bulbs, 
and grafts ;—the life and growth into a new plant of a part 
detached from the trunk ;—the readiness with which they 
throw out new parts, repair what appear to be very serious 
injuries, and adapt themselves to the most unfavourable cir- 
cumstances. The operations of grafting, and of propaga- 
tion by slips and layers, the sprouting of young shoots from 
trunks which have lost their connection with the soil, and 
other well known examples, might be adduced. A plant. 
would seem to be a collection of vital germs united together, 
_ but not necessarily connected, each being capable of a — 
rate existence when placed in a favourable situation. __ 
28. Another peculiarity of plants may be observed in the 
extreme simplicity and uniformity of their internal structure, 
and the small number of separate organs by which their 
functions are carried on. This might be anticipated, since 
we have seen that the vital functions of plants are fewer and 
inferior to those of animals. In animals, we have heart and 
blood-vessels ; brain, spine, and nerves; stomach, and in- 
testinal canal; and several other systems of organs; which, 
differing in a marked degree in structure, point distinctly 
to different vital functions which they perform. Now, dis- 
__ tinctly marked organs, or systems of organs, are fewin plants. 
__ Those performing the most important parts, are spread 
over the whole plant, (as the bark), and are of an uniform 
_ structure every where ; and, such in general is the simpli- a 
_city and minuteness of the organs which carry on the life of 
plants, that we have been unable to acquire a very complete _ = 
eee. of the functions of Ss All the a eee 
