LECT. VIII.] HOLLOW HERBACEOUS STEMS. 425 



in large flattened fasciculi b. b. placed near the 

 cuticle. Immediately beneath the cuticle, round 

 the fasciculi of proper vessels, and bordering the 

 cellular integument interiorly, the cells are irre- 

 gular, smaller than in the centre, and filled with 

 a green secretion, which gives the green colour to 

 the stem; but the colouring matter forming the 

 blotches or maculae is deposited in the cells of the 

 cuticle. Within the cortex, the principal bundles 

 of sap vessels, d. d. with their accompanying de- 

 scending vessels, are placed at equal distances 

 round the circle, and stretch inwards, affording in 

 the transverse section a form not unlike the print 

 of the human foot. These alternate with smaller 

 fasciculi, e. each of which is accompanied by three 

 clusters of descending vessels ; the circumstance 

 in which the peculiarity of this stem consists. 

 The cellular matter is composed of irregular hex- 

 agonal cells, turgid with a colourless mucilaginous 

 fluid, which becomes firm and elastic when the 

 part is placed in cold water. 



The nature of the septum or partition, which 

 interrupts the cavity of the stem at each knot, 

 in this description of stem, is readily seen in a 

 longitudinal section. By the aid of a common 

 lens, the vascular bundles are easily traced, by 

 their whiteness and opacity. Thus in the mar- 

 ginal figure (see next page) the white line a. is a 

 bundle which runs uninterruptedly upwards on 



