HABITS OF PLANTS. 200 



"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." 



Linnaeus enumerated forty-six flowers which possess this kind of 

 sensibility ; he divided them into three classes. 



1. Meteoric flowers, which less accurately observe the hour of fold- 

 ing, but ai-e 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 

 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 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 oflfered 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 life may be changed. Although we may suppose that maify 

 things now necessary to our comfort, and even our fives, 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, we may see lingering 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 climates are gradually accustomed to a lower 

 temperature by placing them in hot-houses, then in green-houses, and 

 lastly, in the open air7 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— Remarlis on their habits of life— Temperature considered ill the na- 

 turalization of plants— Observations necessary in the process. 

 18* 



