436 hiflucnce of Climate on Vegetation. 



Art. VIII. Notes on the Influence oj" Climate on Vegetation, taken 

 at a Lecture hy Professor Lindley on that Subject^ delivered at 



. the Rooms of the Horticultural Society, May 9. 1833. By 

 J. W. L. 



Every one who has paid great attention to plants must be 

 aware that it is as important for their cultivators to know the 

 kind of climate which is natural to them, as it is for them to 

 know the nature of the plants themselves ; yet very few gar- 

 deners have more than general ideas on the subject. They 

 are aware that most exotic plants require heat, but their 

 care of them is generally confined to this particular; and, 

 without considering whether the native climate of a plant be 

 moist or dry, or any other particulars respecting it, they keep 

 their houses hot, and think that they have then done enough. 

 It is no wonder that many plants die under such treatment ; 

 and, that when they live, it is by mere chance, the gardeners 

 not knowing the cause of their own success. 



Nothing can be more variable than the nature of climates. 

 Countries lying under exactly the same degree of latitude 

 have them often essentially different : and it is necessary to 

 know in what these differences consist, to be able to cultivate 

 properly the plants indigenous to each. Before, however, 

 explaining the nature of the climates from which the plants 

 cultivated in British hot-houses are generally brought, it may 

 be advisable to enumerate those points, in all climates what- 

 ever, which operate most strongly upon plants. The principal 

 differences between climates are in their temperature, humidity, 

 air, and light; all of which have a very considerable influence 

 on vegetation. 



Temperature is generally thought to be, and perhaps is, the 

 most essential of all these points. No seeds will germinate 

 under 32° of Fahr. ; and many require at least 60°. Exces- 

 sive cold has a paralysing effect on plants : they droop, be- 

 come languid, their organs contract, evaporation diminishes, 

 and, consequently, by degrees they lose their power of taking 

 food. Too much heat is as fatal to vegetation as too great a 

 degree of cold; and nearly the same effects are produced, 

 though from opposite causes. Excessive heat occasions such 

 rapid evaporation, that the spongioles of the roots are not 

 able to imbibe moisture fast enough to supply it ; the leaves 

 droop, and the plant dies. It is, therefore, clear that a 

 proper temperature is indispensable to healthy vegetation. 

 Temperature acts more on the fluids absorbed by plants than 

 on the vegetable tissue ; and, consequently, plants in a dry state 

 are the least likely to be affected by its changes. 



