98 ON THE "EXPOSURE OF PLANTS. 



level of the sea which determines their hardiness. Many plants 

 are debilitated by confinement in the greenhouse, and very many 

 extra-tropical plants are lost from being placed in what is con- 

 sidered the warmest or most sheltered situation. 



These errors are occasioned either by a want of experience 

 respecting the constitution of the plant, or from inattention to 

 the extreme change of temperature to which it is exposed in its 

 new place, or from ignorance that situation and exposure change 

 the constitution of plants to such a degree that, while one is per- 

 fectly hardy if nursed on a northern aspect, another of the same 

 kind shall be so tender and vulnerable on a southern exposure, 

 that it dies, or is cut down to the ground, under the slightest 

 frost. 



Want of experience concerning the constitution of a newly im- 

 ported plant may be said to be an excusable want of judgement; 

 because we have no means of knowing without experience, there 

 being no general rule to guide. If, indeed, we are told that it 

 is an annual from a warm country, we may safely conclude that 

 it will succeed in this climate during summer, as many tropical 

 annuals do. Or, if it be a perennial herb from the same country, 

 we may find it answer with us if it be only protected from frost. 

 But if tropical shrubs or trees are brought to us, we cannot, from 

 any external mark, judge whether they are liable to be killed by 

 frost or not. If they shed their leaves in winter, it is only a sign 

 that they are winter-restingplants, not that they are hardy ; because 

 tMfce-are several tropical plants which are deciduous", as for in- 

 stance, the silk cotton tree (Bombax ceiba); and many evergreens 

 are as hardy as those that shed their leaves. 

 We often fail in preserving tender plants from inattention to lo- 

 cal circumstances. We are liable to mistake shelter for warmth. 

 Frost and the north and east winds are most dreaded in this coun- 

 try. A southern exposure, whether for the abode of animals, 

 or a station for vegetables, is always considered the most eli- 

 gible, merely, perhaps, because it is the most agreeable to our 

 own perceptions. But in respect of vegetables we often err in 

 this matter, both in choosing sheltered situations and southern 

 exposures. 



Cold (or rather cold air) is always most intense in humid situations, 

 because there is the most copious evaporation. Such situations, 

 in this country, are either on the tops of clayey hills, or in the 

 lowest valleys, where there is either a lake, river, or brook. 



