LKCT. X.] ANATOMY OF LEAVES. 549 



These preparations enable us to trace more readily 

 than in the natural leaf, the divisions, subdivisions, 

 and various ramifications of the vascular fasciculi; 

 but beyond this they afford us no information, and 

 we must have recourse to the microscope to obtain 

 a satisfactory knowledge of the vascular structure 

 of leaves. 



If we commence our investigation with the 

 simplest description of plants, the Lichens and the 

 Mushroom tribe (Fungi) for instance, we perceive, 

 even by the assistance of the best glasses, scarcely 

 any trace of a vascular structure, the whole plants 

 appearing to be little more than an aggregation of 

 cellular substance enclosed in a cuticle. This ap- 

 pearance, however, arises in some degree from the 

 transparency of the vessels preventing them from 

 being distinguished from the cells, and in some de- 

 gree from the simplicity of their structure ; for, as 

 the fluid they convey is not required to be raised to 



use his own expression, sometimes made sad havoc with the 

 solid parts also, he soon dismissed them from his service, and 

 employed the method I have described in the text (see his 

 Adversariorum Decas tertia, Amst. 1723-40). Fruits were also 

 prepared by the same method ; and the description of the in- 

 terior structure of a pear, by Du Hamel, illustrated with 

 engravings, may be seen in the Memoires de V Academic des 

 Sciences, An. 1730-32. In the Philosophical Trans. 1730, No. 

 ccccxiv. p. 371, Francis Nicholls gives an account of the ske- 

 leton of a Pear leaf, the network of which he split into two 

 equal layers. 



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