OF VEGETABLES. 
367 
CHAP. XL. 
Of the Vegetable World. — Theory of Vegetation-Ana- 
tomy of Plants — Circulation of the Vegetable Juices — 
Fructification , 8?c. of Plants— Of the Sexual System— 
The Science of Botany — The Classes, Orders, and Ge- 
nera of Linn ecus — The natural Classification of Vege- 
tables — Conclusion. 
In the progress of our examination of the natural world, 
with our illustrious philosopher, we commenced with a slight 
examination of the materials of which this all is composed ; 
we detailed what is generally known of the fot mation, stiuc- 
ture, and principal phenomena of the earth. \Ve took a shot t 
review of man in his various relations and situations; and 
successively passed through the several gradations ot animal 
nature. From that insensible and almost inanimate class of 
beino-s'of which we so lately treated, the transition to the 
vegetable world is easy; a department which presents to the 
casual observer an almost infinite variety— but the variety is 
only external ; the nature, the habits, the manners (if we 
may so express ourselves) of all vegetables nearly resem- 
ble each other, and we must be content with little more than 
mere classification and arrangement, unless we would depart 
from the province of the naturalist, to intrude upon those of 
the chemist, the physician, or the farmer. 
Of the theory of vegetation, or of the growth, propagation, 
and nutriment of vegetables, our knowledge is slight and 
superficial. A close inspection into the structure of plants, 
affords the best ground for reasoning on this subject, and, 
indeed, every thing beyond it is little better than mere fancy 
and conjecture. . 
On makin" a transverse section of a tree, it appears to 
consist of three distinct parts, the bark, the wood, and the 
medulla, or pith. , . . 
I The bark consists ot two parts, the cuticle, and the true 
bark The cuticle of plants affords an external covering to 
all their parts. It consists of numerous layers, easily sepa- 
rable from each other, and of which the fibres are circulai. 
The true bark may be considered as a congeries of cclluhu 
