ANATOMY OP LEAVES. 283 



some in which the cuticle and pulp are completely- 

 destroyed ; whereas the ribs or veins, as they are 

 commonly but erroneously termed, being less suscep- 

 tible of decomposition, remain almost entire, and dis- 

 play the appearance of a beautiful tissue of net-work, 

 more or less complicated. This is the vascular sys- 

 tem of the organ, and the leaf in this state is termed 

 a skeleton lenf. Leaves are frequently thus prepared 

 by maceration in water, when the cuticle becomes ea- 

 sily separable by gentle rubbing and pressure ; and 

 the pulp may then be washed out from between the 

 meshes of the vascular net-work by rinsing in water : 

 and if the operation be carefully performed, the most 

 minute cords of vessels may be preserved. These 

 preparations enable us to trace more readily than in 

 the natural leaf, the divisions, subdivisions, and vari- 

 ous ramifications of the vascular fasciculi ; but be- 

 yond this they afford us no information, and we must 

 have recourse to the microscope to obtain a satisfac- 

 tory 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 percieve, even by the 

 assistance of the best glasses, scarcely any trace of a 

 vascular structure, the whole plant appearing to be 

 little more than an aggregation of cellular substance 

 enclosed in a cuticle. This appearance, however, 

 arises in some degree from the transparency of the ves- 

 sels, preventing them from being distinguished from 

 the cells, and in some degree from the simplicity of 

 their structure ; for, as the fluid they convey is not 

 required to be raised to considerable heights, as in 

 the more perfect plants, the conducting tube is conse- 

 quently more simple. If, however, we take a plant 

 in which the vessels convey a colorless fluid through 

 a colored cellular structure, as, for example, Mar- 



