440 CONSERVATIVE ORGANS. [LECT. VIII. 



an example of the general structure of this di- 

 vision. It is composed of a central part and a 

 very thick bark. Placing a transverse section of 

 the young root under the microscope, we find that 

 the central part consists chiefly of cellular matter 

 postured in a radiated manner, with one large 

 fasciculus of sap vessels in the centre, and several 

 smaller fasciculi interspersed through it, forming 

 nine or ten indistinct, interrupted rays. In the 

 root of the second year, the additional sap vessels 

 appear as an interrupted circle bounding the cen- 

 tral part; and in older roots, as new circles are 

 annually added, the transverse section resembles, 

 in some degree, that of a ligneous stem ; or it ap- 

 pears to consist of a pith, concentric circles of 

 wood traversed by divergent rays, and a bark. In 

 the longitudinal section we perceive that the sap 

 vessels are punctuated, but certainly not spiral; 

 and that the cells are oblong, but not arranged in 

 the symmetrical manner, which characterizes the 

 former division of the roots under examination. 

 Decorticating the root, we perceive, also, that the 

 fasciculi of sap vessels do not run in straight lines, 

 but take a waving course; and by vessels separat- 

 ing from one fasciculus coming in con- 

 tact with those separated from another, 

 the whole appears like a reticulated tex- 

 ture on the surface of the central part 

 (see marginal cut); a circumstance, 

 however, which is not peculiar to this root, but is 



