202 
HABITS OF PLANTS. 
possesses a very peculiar means of sheltering itself from the heat of the sun, as it 
closes entirely whenever the heat becomes excessive. 
308. Linnaeus divided flowers, in reference to their sensibil- 
ity to atmospheric changes, into three classes : 
1. Meteoric flowers^ which less accurately observe the hour 
Df folding, but are expanded sooner or later, according to the 
cloudiness, moisture, or pressure of the atmosphere. 
2. Tropical flowers^ that open in the morning, and close be- 
fore evening every day ; but the hour of their expanding be- 
comes earlier or later, as the length of the day increases or de- 
creases. 
3. Equinoctial flowers^ which open at a certain and exact 
aour of the day, and for the most part close at another deter 
ruinate hour. 
LECTUEE XXXIX. 
EABITS OF PLANTS. ^AGENTS WHICH AFFECT THEIR GROWTH. ^l^HElxi 
HABITATIONS, AND GEOGRAPHICAL SITUATIONS. ELEVATION COR- 
RESPONDING TO LATITUDE. 
309. The constitution of plants and animals seems to fit tJiem 
for particular climates, and for digesting food of a certain kind. 
The plant cannot, like the animal, rove about in search of food 
best suited to its nature, but, fixed in one spot, must receive 
the nourishment that there offers itself. If this nourishment be 
too abundant, the vessels loaded with excess cease to perform 
their accustomed functions, and the plant dies of surfeit j if, on 
the other hand, the food oiFered be too little, or not sufiicicntly 
nourishing, the plant dies of starvation. 
a. Yet plants may be brought to live in chmates, and on food not naturally suited 
to their constitutions; or in other words, their habits of life may be changed. 
Although we may suppose that many things now necessary to our comfort, and 
even our lives, are rendered so by nature ; yet if we reflect a moment, we shall 
see that many of our own wants are the result of habit. The children of poor 
parents run about in the snow with bare feet, and are apparently much more vig- 
orous than the little master and miss whom the winds of heaven are not permitted 
to visit. Why does this difference exist between individuals of the same species ? 
It is owing to habit. Thus, we may see lingering upon the verge of a northern 
winter a nasturtion ; but the same temperature which it bears without injury, 
would at once destroy those of the same species which have only Uved beneath a 
tropical sun. 
310. Ill changing the habit of a plant, or, as it is frequently 
termed, naturalizing it, the temperature is the principal thing 
;J06. Linna?us' division,— 309, Plants fitted for particular climates--*. Remarks on their habits of 
life. — 310. Teinj)crature considered in the naturalization of plants. 
