Keegun : The Fttcies of' our fibres/ Flora. 



canopy will be poorly illuminated b\ the solar radiance, and 

 hence will be checked in development. If side shoots happen to 

 be formed under these circumstances the leaves which bhey carry 



will be obliged to unfold in the shade, and cannot therefore 

 attain the full size and dimensions which they are capable of. 

 In fact, their position will be similar to that frequently seen in 

 some of our densely-clothed trees, where, even in I nne, small 

 blanches in the interior of the crown become completely leafless 

 and even actually wither away, in this way gradually but surely 

 bringing' about a serious diminution of the total embranchment. 



This phenomenon is specially observable in well-grown Horse 

 Chestnut* a native ol the mountains of Tibet, one of the most 

 sun-illumined portions oi the earth. W hat the dense umbrageous 

 canopy of leaves in certain of our specially favoured trees effects 

 in the way of reduction of shoots and branches is effected much 

 more expeditiously and permanently by the huge developments 

 of the frondescence, especially characteristic of many well-known 

 tropical and sub-tropical exotics, i.e., their comparatively large- 

 sized leaves, by casting a bowery umbrage upon the buds, 

 forbids and checks their normal development. Quite otherwise 

 are the conditions under which our forests rejuvenate their 

 foliage and wide-stretch their umbrageous arms — 



All weave on high a verdant roof, 

 That keeps the very sun aloof, 

 Making; a twilight soft and green 

 Within the column'd vaulted scene. 



In order, however, that this impressive effect be produced, the 

 comparative lOwness of the intensity of sunlight in our latitudes 

 necessitates (i) a fall of leaves in autumn ; (2) a relatively small 

 leaf. The shedding- of the autumn leaves exposes the bare 

 wintry boughs to the influx of the brilliant sunrays in the 

 springtime, so stimulative to the dormant vital energies of 

 the buds. It is evident that if the leaves did not fall the 

 shadows cast by the crown, i.e., in its far-stretching and deeply- 

 dissevered dome-like form, would so seriously interfere with the 

 illumination of the interiorly situated buds and shoots, that 

 their full and free development would be checked and they 

 would gradually perish. Whence it would follow that the most 

 characteristic and distinctive feature of our woodland scenery 

 would be destroyed. In our very few evergreen trees on the 

 other hand, the shadows that lower cannot be severe in the case 

 of the Pines, whose foliage gradually disappears from base to 

 summit of the stem, and in the Firs their pyramidal configura- 



Naturalist, 



