EXPLANATION OF THE PLATES. XV11 



Fig. 6. Longitudinal section of a portion of the stem, and a branch 

 of Sambucus nigra; a. the upper part of the trunk, in 

 which c. the pith, occupies the centre ; b. the branch ; d. its 

 pith; e. the wood produced by the branch; /./. two abor- 

 tive buds. (p. 368). 



7. A vertical section of the dark portion of A . fig. 2. : a. the 



cortex, consisting of, 1 . the cuticle ; 2. the cellular integu- 

 ment ; 3. the vascular layer, in which the character of the 

 proper vessels is displayed ; and, 4. the liber or inner bark ; 



b. the half-organized alburnum ; e. to </. the perfect wood, 

 consisting of 5. 5. 5. some porous, others entire small ves- 

 sels ; and 6. large porous vessels (p. 332) ; d. to e. the me- 

 dullary sheath, containing 7. 7. 7. spiral vessels, and 8 ob- 

 long, porous cells ; e, to/, pith; ** fragments of the cells 

 of a divergent layer, (p. 330 406). 



8. A. Fragment of a transverse slice of the trunk of an old 



elder tree: B. the same highly magnified ; a. a. a. a. vessels 

 of the concentric layers ; b. b. b. the concentric layers; 



c. c. c. the divergent layers. 



9. Longitudinal slice, from the shoot of a vine, which was laid 



down to root; a. the pith; b. last year's wood; c. the pre- 

 sent year's wood in its alburnous state ; e. a root protruded 

 from the alburnum. 



10. A. Portion of a thin transverse slice of an old stem of Sy- 



ringa vulgaris: B. the same highly magnified; . various 

 layers of cuticle, the innermost only of which retains its 

 vitality (p. 321); b.b. ligneous layers; c.c. large vessels 

 between the ligneous layers ; d. alburnum. 



11. Twig of Juglans regia split to show the diaphragms which 



constitute its pith. 



PLATE VII. 



1. A. Magnified view of the embryon leaf-bud, in Syringa vul- 

 garis : a. the gem ; b. the lacerated base of the footstalk of 

 the removed leaf: B. the natural size of the above; c. the 

 gem. (p. 38i). 



