472 X. GENERAL REMARKS.' 



intimate connexions seems obvious enough, whether we 

 look to the earth at large or to Britain by itself. 



Each botanist who has devoted much attention to this 

 intricate subject, has his own particular predilections and 

 fancies about the influence of temperature more espe- 

 cially, and the best mode of estimating that influence in 

 its relations to plants. And each can readily pick out 

 facts enough to give a good show of support to his own 

 favorite fancies ; the facts themselves being countless in 

 their numbers and variations, and some of them of course 

 suiting any theory which has a basis oi truth, however 

 partial and inexact it may be in the whole. Near one 

 hundred thousand species, and perhaps almost millions of 

 differences in local situations, and in the proportions be- 

 tween their temperature and humidity, and the dates and 

 durations of either, are an ample stock of facts, among 

 which to seek for evidences and illustrations of climatal 

 hypotheses. 



That existing difi'erences between the climates of dif- 

 ferent countries are largely influential in determining the 

 existing difi'erences between their floras, is usually ad- 

 mitted as a truism ; although quite understood not to be 

 the only cause or condition of their floral diversities. 

 Perhaps the most condensed and obvious illustration of 

 climatal influence on plants, accessible in this country, 

 may be found in the gardens of wealthy amateurs, and in 

 those of the leading tradesmen who raise plants and pro- 

 duce for sale. Their stoves and hothouses exemplify the 

 influence of continued high temperature, with varied de- 

 grees of humidity ; — say, the warmest weeks of an English 

 summer continued through the year. Their conserva- 

 tories or greenhouses exemplify the influence of like 

 climatal conditions in more temperate degrees, and with 

 greater variations of season; — say, the summers of 



