NOTICES OF BOOKS. 157 



subject itself, of the geographic limits of genera, can hardly be said to 

 be discussed in the Chapter; but our author appears to intimate that 

 their areas are more restricted than we should have supposed them 

 to be. 



(To be continued.) 



V 



tempt to Classify them . 



John Gilbert Baker. 



of Great Britain : an At- 



tlieiT Geognostic Relations ; ly 



This, which is a paper read at Glasgow, before the twenty-fifth meet- 

 ing of the British Association with additions, is an attempt, first, to 

 arrange the British flowering plants and "Ferns according to their pre- 

 dilection for certain soils; and secondly, to determine the amount of 

 change that may be effected in species by the soil in which they grow. 

 The Author states that his sketch is based upon the model of the plan 

 pursued in Thurmann's/Essai de Pliytostatique applique a la Chaine 

 flu Jura/ and adds, tliat his principal inducement is the desire to sug- 

 gest inquiry relative to the subject amongst more experienced botanists 



and geologists than himself. 



The attempt is a very meritorious one, and deserves more at the 

 hands of British botanists than is implied by the comments made by 

 those who heard it read at the time, and which Mr. Baker has very 

 candidly appended to his Essay. The Author starts with considering 

 the soils as being primarily divisible into two classes, — those that disin- 

 tegrate easily, and yield an abundant superficial, usually damp detritus, 

 and those which disintegrate with difficulty, and yield a scanty, dry 

 detritus. Every species is considered (and no doubt truly) as being 

 more or less adapted to flourish upon various kinds of soil, just as it is 

 more or less adapted to inhabit various climates. Further, under equal 

 climatic conditions, different species will always more or less confine 

 themselves to one or the other class of soil ; but with change of cli- 

 mate, under equal conditions of soil, certain species disappear, and the 

 remainder are, upon the whole, less restricted to one kind of soil. 

 Thus, passing from a dry climate to a moist one, under equal condi- 

 tions of soil, it is obvious not only that the dry-climate plants will dis- 



botanist reco-nizes genera before he Joes species ; it might indecJ be argi.ed with as 

 much show o! rcnson. that if genera are not more n.tr.ml than speces, the laf rr are 

 not natural at all ! so arbitrary are their limits throughout wh..h- large ^alu^al 

 Onkrs. 



