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. Meteorio flowers^ which less accurately observe the hour 

 i)f 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 

 fiour of the day, and for the most part close at another deter- 

 minate hour. 



LECTUEE XXXIX. 



HABITS OF PLANTS. AGENTS WHICH AFFECT THEIK GROWTH. THEIK 



HABITATIONS, AND GEOGE 

 RESPONDING TO LATITUDE. 



HABITATIONS, AND GEOGRAPHICAL SITUATIONS. ELEVATION COR- 



309. The constitution of plants and animals seems to fit them 

 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 oisurfeit; if, on 

 the other hand, the food offered be too little, or not sufficiently 

 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 Tvords, 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 sliall 

 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 difterence exist between individuals of the same species ? 

 It is owing to habii. Thus, we may see lingering upon the verge of a northern 

 winter a nasturtion; but the same temperature wliich it bears without injury, 

 would at once destroy those of the same species which have only lived beneath a 

 tropical sun. 



310. In changing the habit of a plant, or, as it is frequently 

 termed, naturalizing it, the temperature is the principal thing 



308. LinnsEUs' Jivision.— 309. Plants fitted for particular climates— a. Remarks on tbeir habits of 

 UCtt. — 310. Temperature considered in the naturalization of plants. 



