210 
ELIBITS OF PLANTS. 
it requires, the degree of light which seems necessary, and the kind 
of exposure, as to winds, which appears most favourable. 
Plants vary much in their susceptibility of naturalization. The 
horse-chestnut, which is now common in the middle and northern 
United States, was originally brought from the tropical regions. In 
these regions, however, it usually grows in grounds somewhat above 
the level of the sea, and therefore its habit, as to temperature, ren- 
ders it in some degree fitted for more northern countries. Orange 
and lemon-trees cannot be brought to bear the roughness of our cli- 
mate, without some protection. 
In many cases, perennial plants by this change of climate are con- 
verted into annual ones ; as if fearing the inclemencies of a cold win- 
ter, they pass through their successive stages of existence with ra- 
pidity, and accomplish in one summer what they had been accus- 
tomed to require years to perform. The nasturtion was originally a 
perennial shrub, flourishing without cultivation on the banks of the 
Peruvian streams ; yet, transferred to this country, it is an annual 
herbaceous plant, which completes its term of existence in a few 
months. 
The acclimating of some plants is with difficulty accomplished ; 
and it is by slow removals that they can be made to grow in foreign 
situations. Rice by a slow progress has advanced from Carolina to 
Virginia, and it is now cultivated in New Jersey. The habits of In- 
dian corn, aided by climate and culture, have suffered a still more 
remarkable change. After having been for several years raised in 
Canada, it arrives to perfection in a few weeks, and on that account 
is eniployed by us as an early corn ; but that which has been long 
cultivated in Virginia, will not ripen in a New England summer ; yet 
originally, the early corn of Canada and that of Virginia were the 
same, both in habit and other properties. 
While merely ornamental or curious plants can with difficulty be 
made to vegetate freely in foreign situations, the vegetables most 
useful to man are disseminated and cultivated. The delicate exo- 
tic flowers often disappoint our expectations ; but the wheat, the po- 
tato, and corn, which are also exotics, seldom are withheld from the 
labour of the husbandman. 
Thus should earthly parents, imitating their " Father in heaven," 
first provide their children with what is useful both for body and 
mind, leaving the ornamental to be bestowed or not, as circumsta|i- 
ces may render proper. 
Agents which affect the growth of Plants, 
Of the various substances by which vegetables are nourished, wa- 
ter is thought the most important. Some plants grow and mature 
with their roots immersed in water, without any soil; most of the 
marine plants are of this description. 
Atmospheric air is necessary to the health and vigour of plants ; if 
a plant is placed under a glass into which no air can enter, it withers 
and dies. 
Most plants are found by analysis to contain a certain portion of 
salts, such as nitre, and muriate of soda,* or common salt. It ap- 
pears that the root absorbs them from the soil by which it is nour- 
ished.. 
* According to modern chemistry, chloride of sodium. 
Plants vary in susceptibility of naturalization— Some plants change from perenniai 
to annual-7Rice and Indian-corn— Agents that affect tke growth of plants— Waters 
h .mospheric air — Salts. 
