508 



" It is a curious fact " says Mr. Geyer, " that while the forests are left 

 undisturbed, the remains are always composed of such or such kinds 

 in almost unchanged proportion. Not so when fire has swept over, 

 and has destroyed the pristine races of trees ; then others spring up, 

 which were either not at all there, or in the minority. So, where Fi- 

 nns ponderosa is removed by fire, Abies rubra will fill that place to 

 suffocation ; if, after a few years it is burnt again, another tree takes 

 the place." In Britain we have few opportunities for observing the 

 effect of burning off arborescent species ; but the natural covering of 

 ericaceous shrubs is repeatedly burnt off the Highland mountains, and 

 there the bared ground is soon re-occupied by the very same species; 

 seedlings of Calluna vulgaris, &c., springing up plentifully among the 

 fresh shoots from many undestroyed old roots. Frequently repeated 

 burnings will effect a gradual change from Ericaceae to Cyperaceae 

 and Gramineae, when aided by the presence of sheep ; for explaining 

 which there are obvious mechanical and chemical conditions. It is 

 more difficult to say why, where one species of pine has been destroy- 

 ed by fire, another and different species shall forthwith occupy its 

 room, though a careful observer of Nature would probably detect the 

 true cause of this, if on the spot to seek for it. 



C. 



Correction of a mistake in Mr. Lawson^s " Stray Thoughts^^ in the 

 January No. of the '■ Phyioloyist.'' By Hewett C. Watson, Esq. 



If Mr. Lawson will again refer to the remark of mine in the January 

 number of the ' Phy tologst,' which he has written against on page 417, 

 he will find that he has misconceived the meaning of the sentence. 

 I remarked that something useful might be gleaned from the " poorest 

 contributions among the rambles and visits ;" but I did not say that 

 the rambles and visits are the poorest contributions to the ^Phytolo- 

 gist.' There are valuable contributions to British Botany among that 

 class of papers, though some of them are very trifling. The remark 

 having been misread, Mr. Lawson's strictures upon it fall for want of 

 basis. 



Hewett C. Watson. 



February 21, 1846. 



