326 CONSERVATIVE ORGANS. [LECT. VII, 



longitudinal section, that of a fascis of flexible 

 cords, readily separable from each other, and 

 from the surrounding cellular substance * ; which 

 is condensed where it comes in contact with these 

 bundles. These vessels are supposed to convey 

 downwards the proper juice of the plant, ela- 

 borated from the sap, by the action of the light 

 and air in the leaf; and this opinion is supported 

 by the fact, that it is from them the milky 

 juice of the Fig-tree and the coloured juices of 

 other plants exude, when the stem is trans- 

 versely divided. In some stems, as, for example, 

 that of Laburnum, Cytisus Laburnum, the vascu- 

 lar bundles coalesce, and form nearly one conti- 

 nuous layer or circle around the wood ; and in 

 others, although they do not actually coalesce, 

 yet, they approach so close as almost to assume 

 the same character. As the stem increases, these 

 vascular bundles become impervious, and are 

 pushed outward with the cellular integument, giv- 

 ing place to a new layer which is annually pro- 

 duced. 



4. Inner bark. Immediately under the vascu- 

 lar bundles, we find another layer -f- which consti- 

 tutes the internal boundary of the bark. In the 

 transverse section of the stem of the Horse Ches- 

 nut now before us, it appears under the microscope 



*Vide Plate 6, fig. 7, a. 3. 



t Plate 6, fig. 2, e. and fig. 7, a. 4. 



