100 ON THE EXPOSURE OF PLANTS. 



There is another circumstance not yet adverted to which ope- 

 rates injuriously on tender plants in sunny and sheltered valleys. 

 There, they are sooner affected by the returning warmth and so- 

 lar beams of spring, and hurried into a premature growth long 

 before frosts are over, or the summer temperature confirmed. 

 They are awake -and putting forth their tender leaves and shoots 

 before the exposed residents of the hill are in the least acted on. 

 The first have their sap liquefied and in motion; that of the se- 

 cond is clammy and at rest ; the first suffer because they have to 

 sustain four degrees of frost perhaps, when least prepared for it, 

 while the second have only to bear two degrees, and are other- 

 wise fortified against it. 



The native plants of the frosty regions of Siberia suffer greatly 

 from late frosts when introduced into British gardens, not from 

 the severity of our seasons compared with that of their own, but 

 entirely from the changeableness of the former. In Siberia the 

 winter sets in at once, and the surface of the ground is soon co- 

 vered 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 intermission of mildnessto 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 great- 

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

 must be guarded in some kind of building erected for the pur- 

 pose. Our want of success in attempting to naturalise some exo- 

 tics shrubs and trees, however, may have happened not so much 

 from the constitutional 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 eli- 

 gible 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 



