572 CONSERVATIVE ORGANS. [LECT. X. 



and the principal bundles are united by smaller 

 transverse cords or fasciculi; which form meshes 

 of a rhomboidal figure, all nearly of the same 

 size in the same leaf. 



Passing on to the leaves of Dicotyledons, we 

 find the reticulated structure of the vascular 

 framework more complex and varied, than we 

 have found it in the leaves of the two natural di- 

 visions^ which we have already examined. This is 

 made evident to the unassisted eye by holding up 

 between it and the light any newly expanded leaf ; 

 but it is more beautifully demonstrated in the ske- 

 leton of a full-grown leaf, carefully prepared. In 

 a leaf of the Indian Fig, Ficus religiosus, thus pre- 

 pared (fig. 2, Plate 10), we perceive seven princi- 

 pal costae, springing from each side of the midrib 

 (a.), and extending to the margin of the leaf, where 

 they bend towards its apex, and are enarched or 

 inosculate with one another (b. b. b. b.). From each 

 side of these costae, a series of secondary fasciculi 

 spring, which, inosculating, also, with their oppo- 

 nents, form a secondary set of arches (c. c. c. c.) be- 

 tween each pair of the principal costae ; and inclose 

 a tissue of minute and exquisitely beautiful reticu- 

 lations, the result of the numerous ramifications of 

 the vascular threads, as they divide and subdivide 

 as it were out of a greater into a less. But besides 

 this distribution of these vascular fasciculi, we 

 observe a fascicle (d. d.), proceeding from each 



