564 CONSERVATIVE ORGANS. [LECT. X. 



(18.) cut in the thickness of the leaf, and viewed 

 in the microscope by transmitted light. The cord 

 of spiral vessels (a.) is a few proper vessels sur- 

 rounded by , and a layer of cellular matter in- 

 terposed between it and the large fascicle (c.) 

 of proper vessels. In splitting the leaf, we per- 

 ceive that these vascular fasciculi run in parallel 

 lines (19.), and take the same curves as the mar- 

 gin ; but do not enter into the spines (a. a.), which 

 are of a hard ligneous consistence, and supplied 

 by small threads of vessels given off from the 

 fasciculi nearest to them. The vascular cords do not 

 anastomose in any part of the leaf; and very few 

 transverse threads are perceptible, compared with 

 those which occur in the membranous leaves of this 

 natural order. But besides the vascular fasciculi 

 we find, in this leaf, and other monocotyledonous 

 fleshy leaves, a system of tubular cells, which might 

 be mistaken for vessels, situated immediately un- 

 der the cuticle (17. d.) 9 from which they extend in 

 straight contiguous lines to the cellular parenchy- 

 ma, the chief substance of the leaf. These resemble 

 beaded or moniliform vessels (les vaisseaux en 

 chapelet of Mirbel), and appear to be composed of 

 transparent membranous oblong vesicles, united 

 at their extremities; and are either perforated, 

 or contain small granules sparsely spread over 

 their inner surface ( 1 9. a.). It is probable that 

 these cells are part of the absorbing system by 

 which fleshy plants, such as the Aloe, which grow 



