LECT. X.] ANATOMY OF LEAVES. 563 



stance, nearly in the same manner as the fasciculi 

 in solid monocotyledonous stems. Viewing the sec- 

 tion (16.) through a magnifying lens, we perceive 

 that the fascicles are of different sizes, the largest 

 being in the centre: and, in a portion of it (17.) 

 placed under the microscope, we perceive that the 

 central fasciculi (a.) differ from the others (&.), 

 in their structure as well as size, being composed 

 of a dense cord of spiral vessels, accompanied by a 

 very large bundle of proper vessels, which is sepa- 

 rated from it by a thin layer of cellular substance ; 



whereas the smaller or marginal fascicles appear 

 to be entirely composed of proper vessels. This 

 structure of the central bundles is still more deci- 

 dedly observed, in a very thin longitudinal slice, 



o o 2 



