LECT. X.] ANATOMY OF LEAVES. 577 



cieles, embedded in the cellular substance of the 

 petiole; and five (a. a. a. a. a.) fasciculi of proper 

 vessels occupying the angles of the footstalk, and 

 situated in the bark, or at least exterior to the 

 former and immediately within the cuticle. The 

 compound fasciculi consist, each, of a band of 

 spiral vessels, arranged in rays, and two fasciculi 

 of proper vessels ; one interior, and the other ex- 

 terior to the band of spirals, but both tangent 

 upon it. One of these compound fascicles passes 

 into each leaflet ; and consequently their num- 

 ber, in the common petiole of compound leaves, 

 generally corresponds to that of the leaflets. In 

 compound leaves, however, which have moveable 

 articulations, we perceive that all the separate fas- 

 ciculi are collected into one fasciculus in the arti- 

 culations. Thus, in the common Kidney-bean, Pha- 

 seolus vulgaris, the petiole of which is channelled, 

 with an articulation at the base of the common pe- 

 tiole and, also, at that of each partial petiole, we 

 find that the vascular fasciculi (a.a.b. b. fig. 8, Plate 

 10) are distinct, and form a circle situated immedi- 

 ately under the bark in the channelled parts of the 

 petiole ; with a considerable portion of lax cellular 

 substance or medulla (c.), enclosed within the circle 

 which they form : whereas, in the articulated parts, 

 there is one central fasciculus only (a. fig. 7, Plate 

 10), surrounded by a large mass (b.) of very firm 

 cellular matter. The advantage of this change of 

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