USES OF LEAVES. 137 



surfaces of the leaf. Holman detected and separated 

 them in the leaf of the Pear tree, and Linnseus pursuing 

 the same inquiry discovered their points of union, and 

 ascertained that the fabric of the inferior layer is more 

 delicate than the other. It is said that Hedwig discov- 

 ered similar layers in the mosses which he examined, 

 and moreover, that in the leaf of the Orange tree, he 

 detected an additional layer. " But no language is 

 able to convey an adequate idea of the delicacy and 

 intricacy of the web. It must be inspected as it exists 

 in the contexture or rather in the decay of the leaf, 

 whole leaves being found reduced to a skeleton of 

 fibres in the winter or spring, lying at the roots of 

 trees in situations where they have not been dispersed 

 by the wind."* Figs. 57 and 58 represent the cor- 

 tical net 



12. USES OF LEAVES. 



Wearied with the examination of the diversified 

 forms of leaves, the student turns with delight to the 

 contemplation of their uses, and in the pursuit of the 

 latter inquiry, he finds an adequate compensation for 

 the fatigue of the former. 



It was the opinion of an ancient writer, that leaves 

 were designed to protect fruit from the intense heat of 

 summer. In proof of its correctness, he observed that 

 leaves always appear before the fruit, continue till it 

 ripens, when they fall, as if the sole end of their exist- 

 ence was accomplished. If however, a branch be 

 prematurely stripped of its leaves, its green fruit will 

 never arrive at maturity. It was also observed, that in, 



* Keith. 



* 13 



