74 Dr Fleming's Remarks on the Defoliation of Trees. 



regularly all their functions, and drop off when they cease to 

 act their part in the economy of the plant. But when the 

 beech is trained in a hedge, it is too much shaded, the buds 

 seldom attain their true size, and the leaf is frequently destroy- 

 ed by cold, previous to the end which it is destined to serve 

 having been accomplished. 



In some cases, leaves, which naturally would fall off in 

 autumn, continue, when the plant is subjected to the shears, to 

 outlive the winter, — as the privet. The leaves, under such 

 circumstances, may be said, in the language of farmers, to be 

 " kept back," and to be capable of resisting the cold, while use- 

 ful to the economy of the plant. Many analogous examples 

 occur among herbaceous plants. 



In the trees with deciduous leaves, it is probable, that, dur- 

 ing the period of their nakedness, the bark may be viewed as 

 the aerating organ, destined to effect the escape of the super- 

 fluous carbon from the system. During this period, they may 

 be viewed as resembling " plantce aphyllce."" The bark, in- 

 deed, of the young shoots of several trees and shrubs, as the 

 common broom, is so very like, in colour and texture, to the 

 leaves, as to render it, in all probability, fit to supply their 

 place for a time. 



In trees of the second class, the leaf may be termed "foli- 

 um annuum.' 1 '' It exercises its functions until a new set of 

 leaves be produced, and is then cast off in the ordinary order 

 of seniority. Many of our most ornamental evergreens are of 

 this description, as the bay, laurel, ivy and holly. These are 

 termed evergreens, because the plant is never left naked, and 

 the leaves of this year exercise their functions, and preserve 

 their colour, until the shoots of the following season have ac- 

 quired their clothing. The leaves of the plants of this class, 

 appear, therefore, to exercise a greater influence, in the eco- 

 nomy of vegetation, than in those connected with the first. 

 Here the plant requires the aid of leaves at all times, no other 

 organs, in ordinary cases, appearing to be capable of exercis- 

 ing their functions, or acting as a substitute. Do these annual 

 leaves exercise a greater variety of functions than the decidu- 

 ous leaves ? Or does the bark of a tree, with annual leaves, 



