574 CONSERVATIVE ORGANS. [LECT. X. 



simple and to compound leaves, as far, at least, as 

 respects the expansion. In sessile leaves, how- 

 ever, all the fasciculi do not proceed from the 

 midrib, but some are given off directly from the 

 stem or the branch, and enter the expansion of the 

 leaf at its base, on each side of the midrib. In 

 petiolated leaves, also, the petiole is generally 

 dilated at its point of union with the branch, and 

 at this point the vessels enter the petiole in distinct 

 bundles ; the remains of which are visible in the 

 eschar produced by the falling of the leaves in 

 autumn. 



Thus in the Apple, the Pear, the Peach, and 

 many other trees, the leaf is attached to the 

 wood by three fasciculi, one of which enters the 

 middle of the petiole, and the others on each side 

 of it. In the Lilac, the attachment is also by 

 three distinct fasciculi ; but there is besides a line 

 of coalesced fasciculi which forms a kind of open 

 crescent; and in the Laurustine the whole of the 

 vessels pass from the wood into the petiole in one 

 fascicle, the transverse section of which is nearly 

 a complete semicircle. In compound leaves, the 

 number of fasciculi passing into the petiole from 

 the wood, is in some instances regulated by the 

 number of the leaflets; in the Elder, we find 

 generally five ; and in the Horse Chesnut, from 

 five to seven or eight. It is, however, the inner 

 part only of these fasciculi, or that which con- 



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