186 REVIEWS. [August, 



the same soil. The well-known fact that when a natural forest 

 is cut down, trees of different species commonly spring up in the 

 room of those destroyed, is adduced in proof of the necessity of 

 rotation ; and the hypothesis of the elder De Candolle, that roots 

 discharge excretory matter, so as to poison the soil for them- 

 selves, is dwelt upon as an established fact." 



Some may be inclined to doubt the facts assumed, and to aver 

 that they are other than well-known or established. But the fol- 

 lowing facts are indisputable, viz. that " in the hands of some 

 writers who establish new species ' on every local race, if it differ 

 by a hair's breadth from their "typical" form,' a chapter like the 

 present (on the area or space on the surface of the globe over 

 which a species extends) would only lead to confusion. Fortu- 

 nately for science M. de Candolle is content to call ' Ranunculus 

 aquatilis' by its single narhe, and consequently finds it to extend 

 over the northern hemisphere, from Lapland to Abyssinia, and 

 from the 68th parallel of north latitude in America to California. 

 Had he chosen the opposite course, he might easily have treated 

 us to a crowd of ' representative species,' each peculiar to its own 

 pond or ditch over the same extent of surface." On this passage 

 and on this fact we leave our readers to make their own com- 

 ments. 



We have not room for the fifty regions of the earth, each one 

 supposed to indicate a more or less marked flora. To this sub- 

 ject the attention of our readers will be called in subsequent 

 articles on this interesting subject. The following facts are suf- 

 ficiently remarkable to merit notice at this time and in this place. 

 It is well known that only one plant in 800 is common to both 

 Australia and Europe; it is not however so generally known 

 that upwards of a sixth part of the plants of New Zealand are 

 also European species. In Australia in 1814 the plants of New 

 Holland were reckoned at 3700 flowering species, of which 45, 

 just -g4-o part, were also Europeans. In the smaller islfind of 

 New Zealand the numbers in 1856 were 730 ; and 60, nearly 

 one-twelfth, were also European plants. 



The following facts are still more remarkable. Of the 113 

 Nbrfolk Island plants 61 are peculiar to that locality, or are 

 found nowhere else. Tristan da Cunha contains 33 species of 

 flowering plants, of which 26 are peculiar to that small isle. 



Another series of facts illustrated by this indefatigable observer 



