LECT. VII.] ANATOMY OF 8TEMS. 319 



the outer being the unorganized pellicle of true 

 epidermis, and the inner a vascular texture, com- 

 posed of minute vessels which terminate externally 

 at the surface of the stem, and internally in the 

 cellular integument *. These are, apparently, an- 

 nular vessels with oblong pores ; and, although 

 I have never been able completely to satisfy myself 

 that they penetrate the real epidermis, yet, they 

 probably do so to perform the office of exhalants 

 or of absorbents. The abrupt manner in which 

 these vessels terminate in the cellular integument, 

 readily accounts for the facility with which the 

 cuticle separates from that portion of the bark -f-. 

 Such is the cuticular portion of the bark of the 

 Horse Chesnut ; but the structure of this part 

 is not the same in all ligneous dicotyledonous 

 stems. In that of the Pear, Pyrus communis, it 

 consists rather of transverse cells than of vessels, 

 the outer series of which is covered by the real 

 epidermis: this is the case also in the lesser Pe- 

 riwinkle, Vinca minor, in which there are three 

 series of such cells ; in the Laburnum, Cytisus 



* Vide Plate 6, fig. 2, a. 



f It was probably this vascular part of the cuticle, which 

 led Du Hamel (Phys. des Arbres, liv. 1. c. ii.) to describe the 

 vegetable epidermis as a tissue of delicate parallel fibres inos- 

 culating at regular intervals, or united by lateral fibres, so as 

 to constitute a network, the meshes of which are filled up 

 with a thin, transparent pellicle. 



