420 CONSERVATIVE ORGANS. [LECT. VIII. 



tinuity the first concentric woody circle in a ligne- 

 ous stem, and 3. a cellular pulp, c. which gra- 

 dually loses its aqueous contents, and assumes the 

 characters of a- real pith. By the aid of the mi- 

 croscope, we find that the cuticle consists of a 

 thin, transparent, cribriform membrane ; and en- 

 closes a cellular cortex (Plate 8, fig. 6, B.), the se- 

 cond layer of the cells of which a. is filled 'with 

 a green coloured fluid, which extends over four 

 or five layers at each angle, and is the source 

 of the colour of the stem. Beneath this green 

 secretion the cells contain a pale yellow fluid, 

 which gradually deepens towards the interior of 

 the cortex, where we find its source, the proper 

 juice, filling a range of narrow oblong cells b. 

 which are situated close to c. the layer of return- 

 ing vessels. In these, the proper juice is much 

 paler than in the adjoining cells, which is pro- 

 bably owing to its dilution, in consequence of the 

 greater fluidity which is necessary for permitting its 

 motion in the vessels, through the cribriform 

 coats of which it passes into the adjoining cells, 

 where it is inspissated by rest, slowly spreading 

 its colour outwards by the lateral communication 

 of the cells. In d. which may be termed the 

 woody layer, and which consists of the large or 

 sap vessels embedded in a green pulp, we find 

 the vessels arranged like wedges pointing in- 

 wards, separated by cellular septa, and thus form- 

 ing a continuous band enclosing the cellular pa- 



