NATURAL HISTORY OF PLANTS. S? 



Plants, like animals, are confined to certain latitudes. Many 

 natives of warm countries can, by degrees, accustom themselves to 

 our climate, and even to those that are colder. Uuder-shrubs are 

 more easily reconciled to a warm than a cold or even a temperate 

 climate. In high latitudes there foils at the beginning of winter a 

 deep snow, that does not melt till the return of spring, after which, 

 no night frosts are to be expected, and the air of which is but a de- 

 gree of temperature above the freezing point. In temperate cli- 

 mates, it often freezes strongly without snow having previously 

 fallen, and thus the plants are killed. By this means the polar 

 and alpine plants, which in their native places are covered with 

 snow, are frozen with us, where frosts without snow are frequent. 

 It is only those uuder-shrubs and annual plants of warm countries, 

 which require a longer time for pushing their shoots and flowers than 

 the short summer of a cold climate permits, that cannot here be 

 inured to the open air, and those which require a great degree of 

 heat. 



But trees and shrubs seem to be more sensible of cold, because 

 their perennial trunk is raised high above the ground, and thus 

 sooner suffers by the vicissitudes of the weather. Some that are na- 

 tives of warm climates have become naturalized with us, perhaps 

 because their cellular texture is tougher than that of other plants ; 

 but, on the contrary, there are many, that in this respect are unac- 

 commodating, because their organization will endure no great alter*, 

 nation of heat and cold. 



But the most useful plants, like the domestic animals, are capable 

 of succeeding in very different climates. If there are some which 

 are confined to certain zones, there are others in those regions 

 where these cannot live, to supply their places. Under the equator 

 and within the tropics in similar situations, our kinds of grain do not 

 prosper : but, instead of them, there are the rice, (Oryza sativa), 

 Indian sorn, (Holcus Sorghum), and Turkey corn, (Zea Mays), 

 which are proper substitutes for our grain. Tn Iceland and Green- 

 land neither our corn nor that of the tropical regions will grow ; 

 but nature has provided for these countries the Elymus arenarius, 

 in abundance, which, in case of necessity, may be used as rye. 



In no cold climate are there wanting esculent roots and pulse. 

 Of these many grow wild which remain untried, but of which ne- 

 cessity, if we had not received our garden plants from the East, 



P3 



