LECT. VIII.] ORIGIN OF BRANCHES. 387 



branch can be traced; for it is now obscurely 

 marked by the deposition of alburnous matter, 

 which being paler and more transparent than the 

 rest of the bud, is seen separating the cellular 

 substance to constitute the future pith (see Plate 

 7, fig. 6, .), from (b.) that which is to form the 

 bark. But no spiral vessels are yet perceptible; 

 the alburnous circle is mere semitransparent mat- 

 ter ; and the pith is distinguishable from the cel- 

 lular substance in which the germ is formed only 

 by the paler alburnous matter surrounding it*. 

 The progress of the organization advances a little 

 in autumn ; but is not perceptible during winter, 

 and it is not until the following spring that the 

 embryon branch is very conspicuous. At this 

 period, in the Lilac, the plant before us, it is seen 

 rising as it were from the medullary sheath, in 

 which the spiral vessels seem to originate ; and 



* In this figure { Plate 7, fig. 6) the germ d. is seen separat- 

 ing the exterior scales c. which were originally the lobes. It 

 appears to consist of the rudiments of four leaves, which are 

 not, however, the true leaves ; but those intermediate between 

 the lobular scales and them, the true leaves being yet latent. 

 The pith of the new branch originates from a. : the pale space 

 between this and b., the bark of the embryon branch, is alburnous 

 matter : e. is the eschar, formed by the fall of the leaf in au- 

 tumn, with the spiral vessels which supplied the leaf, now ob- 

 structed ; f. the rudiment of a spiral vessel belonging to the 

 scale c. ; g. the bark of the portion of the shoot above the 

 bud ; h. the alburnum ; . the medullary sheath j k. the medulla, 



cc2 



