24-2 PHYSIOLOGICAL BOTANY. PART II. 



distinct from the two already explained, which con- 

 siders the vegetable individual, in the most usual ac- 

 ceptation of the term, as an entire plant which has 

 originated from the development of a single seed. But 

 this definition of an individual involves the seeming 

 absurdity, that an organised being may consist of several 

 detached portions, each of which may exist apart from 

 the others. Thus a cutting from a tree is a part of 

 the individual from whence it was taken ; and though 

 it may also become a tree, it is no more than the 

 developed state of a portion of the former. Since all 

 the weeping willows in Europe, for instance, are said 

 to have originated from cuttings taken from a single 

 tree; according to this hypothesis, there is no more than 

 one weeping willow in Europe, and that also can only 

 be a portion of one which may be still growing in Asia. 

 But whatever be the speculations of physiologists, we 

 must admit the truth of the remark, " that in ordinary 

 parlance we require some more precise mode of express- 

 ing ourselves, when we would speak of the individual 

 weeping willow which shades the grave of Napoleon 

 at St. Helena, as being the same plant which decorates 

 the tomb of J. J. Rousseau at Ermenonville, although 

 each may probably have originated from the same em- 

 bryo." But if we cannot, in the present state of know- 

 ledge, exactly determine the requisites which constitute 

 the individuality of vegetables, and may possibly con- 

 sider as a separate existence what in reality constitutes 

 the duration of a succession of individuals ; yet whilst 

 we choose to put such a limitation to our ideas, we may 

 speak of the duration of life in a plant as the real ex- 

 istence of an individual, whether this plant may have 

 originated from a seed, bud, cutting, or from any other 

 mode by which it could be propagated. 



(239.) Longevity of Trees. When we consider each 

 separate plant as an individual being, there is this ma- 

 nifest and important distinction between the mode in 

 which its life is maintained, and that in which it is 

 continued in any animal ; the plant annually renews 



