128 ON THE EXPOSURE OF PLANTS. 



severity of our seasons compared with that of their own, but en- 

 tirely from the changeableness of the former. In Siberia the winter 

 sets in at once, and the surface of the ground is soon covered with 

 snow ; every vegetable becomes instantly torpid, and in this state 

 remains in perfect safety till the return of spring, or rather summer, 

 as there is scarcely any spring season in that northern clime — no in- 

 termission of mildness to excite, and frosts to destroy the tender 

 plants, as is so often experienced in this country. 



The changeableness of our spring weather is, in fact, the greatsst 

 bar to our possessing very many plants, which, to have at all, must 

 be guarded in some kind of building erected for the purpose. Our 

 want of success in attempting to naturalise some exotics, shrubs and 

 trees, however, may have happened not so much from the constitu- 

 tional delicacy of the plants themselves, as to the injudicious manner, 

 perhaps, in which the trial has been made. Exposed situations on 

 the north side of a hill, and on poor and dry, rather than on rich and 

 moist soil, is certainly the most eligible station for making a trial of 

 the constitution of a foreign plant. Here it would not be excited into 

 too early growth by the early sun of the day or of the season, nor 

 would the aspect induce precocious growth. Its growth would be 

 slower, but its shoots would be firmer in texture, and consequently 

 better able to resist the destructive effects of frozen sap. 



I cannot conclude these observations without first alluding to the 

 ideas entertained about the acclimatation of exotic plants. The 

 notion is founded on the supposition that, as animals have a tendency 

 to accommodate themselves to foreign climates, or to the changes of 

 temperature of their own native place, so plants may in like manner 

 be susceptible of physical changes which would enable them to bear 

 great diversity of climatal temperature; but, from all experience on 

 this point, it appears, from many tropical annuals long cultivated in 

 Britain, that they have not perceptibly advanced in hardihood since 

 the first day of their introduction. Such are the runner kidney-bean 

 (which, by the bye, is a perennial) ; the potato and cucumber among 

 culinary vegetables ; the China aster and balsam among flowers, and 

 the melon among fruits. All these have been perpetuated by seeds 

 that have been produced, ever since their first introduction into this 

 country, but without gaining any additional protective habit against 

 frost. "We may, therefore, conclude that plants generally have been 



