SEAT OF VEGETABLE LIFE. 133 



and increase in size, though the cavity would never 

 again be filled up. 



There are, therefore, it is necessary to repeat, two 

 states or degrees of vegetable life which should be 

 described in order to be distinguished from each other, 

 to avoid confusion of terms or ideas. The first is 

 always present in those members which are capable of 

 amplification, or are in the act of accretion, i. e. ex- 

 panding from a small to a larger volume. The 

 second is that state in which it is only conservative, 

 but without the power of further growth of the mem- 

 bers preserved by it. The first it is deemed proper 

 to designate by the name of vital envelope^ whence 

 proceeds every new member of trees, shrubs, and many 

 herbaceous plants. The second is that state of the 

 bark and alburnum which, having but recently come 

 into full form and magnitude, serve as conductors of 

 the fluids of the system for a certain time, but from 

 which the actual life has for ever fled. 



Where then does the living principle reside ? In 

 the pith ? no : in the wood, or in the bark ? no, in 

 neither of these, but it is always found at all times be- 

 tween the liber and the alburnum, slightly attached to 

 both, but united to neither : it is reasonable, there- 

 fore, to conclude, that it is a distinct member of the 

 system. 



Of these opinions it is necessary to bring forward 

 proof; and in order to do so satisfactorily, we have 

 only to trace the phenomena of vegetation through 

 the spring' and summer growth of a tree of a few years 

 old. 





