6g 



THE FACIES OF OUR FOREST FLORA. 



P. Q. KEEGAN, LL.D., 



Patterdale, Westmorland. 



By those who perpetually reside in temperate climes the charac- 

 teristic facies, so to speak, of our sylvan scenery is not fully 

 appreciated ; that is to say, it is not sufficiently considered or 

 envisaged as to its special scientific aspects and meaning. The 

 very familiarity of the ordinary appearance of our native and 

 denizen trees and shrubs induces a practical ignorance or rather, 

 perhaps, an unconscious ignoring of the actual and efficient 

 causes and agencies which have served to bring it about. 

 When, for example, we compare the huge leaves, evergreen as 

 a rule, of some of the conspicuous types of tropical vegetation 

 with the tiny foliaged and deciduous clothing of our forests, we 

 must needs be led to suppose or conclude that some powerful 

 agency is operative to produce effects so diametrically opposite. 

 What this special agency is, it is now our purpose to specifically 

 demonstrate. 



The effects of the intensity, brightness, refrangibility, and 

 colour of the solar radiance have been pretty thoroughly studied 

 and examined as regards their respective influences on the 

 vegetation of a district in general or on that of a certain species 

 of plant in particular. One thing, however, is absolutely 

 certain, viz., that the differences between the tropics, where 

 a very high and approximately equal intensity of light prevails 

 all the year round, and our own temperate zone, where the light 

 is never very intense and is decidedly intermittent, have super- 

 induced distinctive characters on the plants submitted to these 

 two conditions of illumination respectively. These characters 

 are exhibited in the general umbrageousness or otherwise of the 

 foliage, the ramification, the spray, the number of buds that 

 burst their cerements or remain dormant, the number of 

 branches and leaves annually produced, and, above all, the com- 

 parative size and configuration of those leaves. The most 

 pregnant consideration is this. On superficial contemplation it 

 might be imagined that the trees growing in the tropics, being 

 evergreen and therefore deprived of a periodical winter rest, 

 enjoy a longer time and more favourable conditions for the 

 development of shoots both terminal and lateral, than do the 

 trees of temperate latitudes. In order, however, that a shoot 



1901 March 1. 



