IV. CLIMATE. 107 



summer heat of the more equal climate would prove 

 inadequate to develope and mature some plants, such as 

 would flourish under the less equal or " excessive " cli- 

 mate, because i-equiring higher warmth and bearing 

 greater cold. On the contrary, the cooler summer of the 

 more equal climate might still be sufficient for other 

 species, which would be destroyed by the greater in- 

 tensity of cold in the excessive climate. Numerous facts 

 have been observed which bear out this hypothetical 

 case ; here given only for the sake of showing the dis- 

 tinction, and not as being in itself a literal fact. Hence 

 it becomes important to phyto-geographers, to ascertain 

 the diff"erence of temperature according to season. It is 

 to be remarked, however, that even in thus taking the 

 temperatures of the seasons separately, the tendency to a 

 reduction of the higher temperatures, by averaging them 

 with the lower temperatures, is only abated without being 

 fully removed. An inland locality, warmer by day and^ 

 cooler by night, might have the same summer mean as 

 another locality on the coast, with the day and night tem- 

 peratures more equal. The former might in consequence 

 be adapted to mature plants, for which the less warm days 

 of the latter would be insufficient. Perhaps eventually 

 the best comparisons may be made for purposes of phyto- 

 geography, by ascertaining the average number of days 

 on which the thermometer indicates given degi'ees of 

 temperature ; for instance, above 50, 60, 70, 80, and 

 intermediate numbers. These would be good data to- 

 wards comparing the climatal force (so to express it) of 

 difi'erent places, or of different years at the same place. 

 At present such data are not attainable, unless imper- 

 fectly, and at a sacrifice of time greater than can be 

 devoted thereto. So that, the usual manner must here 



