402 CONSERVATIVE ORGANS. [LECT. VIII. 



which it appears, but is not always evolved in the 

 season in which it is generated. When it appears 

 at any future time, therefore, although it is, as 

 I have demonstrated, traceable from the medul- 

 lary sheath to the surface on which it appears, 

 yet, the maintaining a communication with that 

 sheath has long ceased to be requisite, either for 

 its preservation or its nourishment ; and, conse- 

 quently, it is not affected by the destruction 

 of that part, or of the circles of wood interme- 

 diate to it and the bark. The pale streams of pa- 

 renchyma traversing these circles, only mark the 

 track in which the vital speck or germ has ad- 

 vanced to the surface of each annual zone, where 

 it was ready to be developed, had circumstances 

 been favourable for that event ; but this streak of 

 parenchyma is altogether useless as far as regards 

 the gem, except in the zone on the surface of 

 which it is seated, and with the life of which its 

 vitality is, indeed, intimately connected. De- 

 stroy this zone, and the latent germ becomes 

 extinct; increase its vital energy by any means, 

 as, for example, by lopping off a branch, and 

 the germ is evolved into a perfect bud and 

 branch; but leave the parts as they are, and 

 the vital speck advances to the surface of the next 

 zone which is formed over the present, and so on 

 progressively, until it is ultimately evolved, or 

 perishes with the destruction of the tree. The bud, 

 therefore, which appears on the surface of a hoi- 



