HABITS OF PLANTS, 
209 
" The flower of the dandelion possesses very peculiar means of 
sheltering itself from the heat of the sun, as it closes entirely when- 
ever the heat becomes excessive." 
Linneeus enumerated forty-six flowers which possess this kind of 
sensibility ; he divided them into three classes. 
1. Meteoric jiowers^ which less accurately observe the hour of fold- 
ing, 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 before 
evening every day, but the hour of their expanding becomes earlier 
or later, as the length of the day increases or decreases. 
3. Equinoctial flowers^ which open at a certain and exact hour of 
the day, and for the most part close at another determinate hour. 
LECtURE XL. 
HABITS OF PLANTS — AGENTS WHICH AFFECT THEIR GROWTH THEIR HABITA- 
TIONS, AND GEOGRAPHICAL SITUATIONS — ELEVATION CORRESPONDING TO 
LATITUDE. 
The constitution of plants and animals seems to fit them for par- 
ticular climates, and for digesting food of a certain kind. The plant 
€annot, 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 is too abundant, the vessels 
becoming loaded with excess, cease to perform their accustomed 
functions, and the plant dies of surfeit ; if, on the other hand, the 
food offered is too little, or not sufficiently nourishing, the plant dies 
of starvation. 
Yet plants may be brought to live in climates, and on food, not 
naturally suited to their constitutions ; or in other words, their habits 
of hfe may be changed. Although we may suppose that many 
things now necessary to our comfort, and even our lives, are ren- 
dered so by nature ; yet if we reflect a moment, we shall see that 
many of our own wants are the result of habit. Did you never see 
the children of poor parents running about in the snow with bare 
feet, and apparently much more vigorous than the little master and 
miss whom the winds of heaven are not permitted to visit too roughly ? 
Why does this difference exist between individuals of the same spe- 
cies? It is owing to habit. Thus, w^e may see hngering upon the 
verge of a northern winter, the nasturtion ; but the same tempera- 
ture which it bears without injury, would at once destroy those of 
the same species which have only lived beneath a tropical sun. 
In changing the habit of a plant, or, as it is frequently termed, na- 
turalizing it. the temperature is the principal thing to be considered; 
although the soil and the quantity of moisture should be rendered as 
similar as possible to those of its native habitation. 
Plants from warm chmates are gradually accustomed to a lower 
temperature by placing them in hot-houses, then in green-houses, and 
lastly, in the open air. While the plant is going through with this 
kind of discipline, an opportunity is afforded of observing the kind 
of soil most favourable to its growth, the quantity of moisture which 
Meteoric flowers— Tropical— Equinoctial— The constitution of plants fitted for par- 
ticular climates— Remarks on their habits of life— Temperature considered in the na- 
turalization of plants- Observations necessary in the process. 
