LECT. VIII.] ORIGIN OF BRANCHES. 399 



but the first part that can be distinctly recognised 

 is the pith, which, in a longitudinal section of the 

 green twig of the Lilac, made three weeks after its 

 protrusion from the bud, and the appearance of 

 the gem on its surface, resembles a more opaque 

 spot of a greenish hue ; with lines running in a 

 direction from the centre of the parent branch to- 

 wards the apex of the gem. These are the first 

 traces of the spiral vessels of the future branch 

 (see Plate 7, fig. 9, a.). The cellular matter, in 

 the part of the bud above the vital speck, which 

 now appears as at c. displays also at this period a 

 more regular form, and indications of its separa- 

 tion into scales are already perceptible at b. ; but 

 the whole bud is still a completely insulated body. 

 As the organization proceeds, new scales are seen 

 separating from the mass of parenchyma, the 

 medulla enlarges in every direction, and in au- 

 tumn the whole presents a pyramidal appear- 

 ance ; in which state the bud remains nearly sta- 

 tionary until the ensuing spring. 



As the cessation of the vegetative power in 

 winter increases in a great degree the excitability 

 of plants which outlive its severity, the genial in- 

 fluence of spring is very early visible on their 

 buds, in which the whole vital energy of trees and 

 shrubs may be supposed at this period to reside; 

 and it is only by the visible change which rapidly 

 occurs in them, that we can pronounce upon the 



