INDIVIDUALITY: SENESCENCE 461 



and greatly extended, by the gardener, who, besides all the 

 methods of cutting, layering, and so on, has in his hands the 

 possibilities of grafting and budding. 



Individuality. — In all cases of vegetative multiplication 

 it is a matter of difficulty to decide where one individual 

 ends and another begins. We can root a cutting from a 

 willow, but is the plant so obtained really any more an 

 independent individual than the other shoots which we left 

 on the tree ? The rhizome of an anemone branches ; while 

 the parent rhizome lives the branches are undoubtedly part 

 of it ; do they become new individuals just because it dies 

 away ? We can define the individual as the product of a 

 reproductive cell ; but we have restricted the term " repro- 

 duction " to these cases in which a fresh start is made with 

 the highly specialised spore or zygote. If we hold to this, 

 and it seems the only logical course, we exclude vegetative 

 multiplication from the conception of reproduction, and we 

 deny the rank of individual to the separate plants produced 

 by it. The products of the original vegetative point, whether 

 they remain attached to a parent stem, or separate from it 

 in a thousand parts, are members of one individual. 



Senescence. — This conception has the further advantage 

 that it focuses our attention once more on the significance 

 of sexual reproduction. If the sexual process has some 

 necessary rejuvenating action, we should expect to find the 

 span of life of one of the " greater individuals " restricted, 

 as is the span of a tree. The evidence is conflicting, but on 

 the whole tells against any limitation whatever. On the 

 one side we have the belief, never sufficiently investigated, 

 that fruit trees degenerate after a certain period of propaga- 

 tion by grafting ; and that many cultivated plants, usually 

 propagated vegetatively, such as the potato and the sugar- 

 cane, are very subject to disease. Pallis (191 6) believes that 

 in the " plav," the great floating reed-swamp of the Danube, 

 the masses of rhizome show a distinct succession, ending, 

 after a period of vegetative multiplication, in the production 

 of stunted shoots, senility, and death. Benedict (191 5) has 

 given evidence that the amount of assimilating tissue in vine 



