196 Prof. Asa Gray on the Que.tti'on 



and have lost none of their force since. Weeping willows, 

 bread-fruits, bananas, sugar-cane, tiger lilies, Jerusalem arti- 

 chokes, and the like have been proj)agated for a long while in 

 this way without evident decadence. 



Moreover the analogy upon which his hy|)othesis is founded 

 will not hold. Whether or not one adopts the present writer's 

 conception, that individuality is not actually reached or main- 

 tained in the vegetable world, it is clear enough that a connnon 

 plant or tree is not an individual in the sense that a horse or 

 man, or any one of the higiier animals, is — that it is an indi- 

 vidual only in the sense that a branching zoophyte or mass of 

 coral is. Solvitur crescendo : the tree and tlic branch equally 

 demonstrate that they are not individuals, by being divided 

 with impunity and advantage, with no loss of life, but much 

 increase. It looks odd enough to see a writer like Mr. Sisley 

 reproducing the old hypothesis in so bare a form as this — " I 

 am prepared to maintain that varieties are individuals, and 

 that as they are born they must die, like other individuals." 

 " We know that oaks, sequoias, and other trees live several 

 centuries ; but how many, we do not exactly know. But that 

 they must die, no one in his senses will dispute." Now what 

 people in their senses do dispute is, not that the tree will die, 

 but that other trees, established from cuttings of it, will die 

 with it. 



But does it follow from this that non-sexually propagated 

 varieties are endowed with the same power of unlimited dura- 

 tion that are possessed by varieties and species propagated 

 sexually (?'. e. by seed) ? Those who think so jump too soon at 

 their conclusion. For, as to the facts, it is not enough to 

 point out the diseases or the trouble in the soil or the atmo- 

 sphere to which certain old fniits are succumbing, nor to prove 

 that a parasitic fungus {Peronospora infestans) is what is the 

 matter with potatoes. For how else would constitutional 

 debility, if such there be, more naturally manifest itself thaii 

 in such increased liability or diminished resistance to such 

 attacks ? And if you say that anyhow such vaineties no not 

 die of old age (meaning that each individual attacked does not 

 die of old age, but of manifest disease), it may be asked in 

 return, What individual man ever dies of old age in any other 

 sense than of a similar inability to resist invasions which in 

 earlier years would have produced no noticeable effect ? Aged 

 people die of a sliglit cold or a slight accident ; but the inevit- 

 able weakness that attends old age is wliat makes these slight 

 attacks fatal. 



Finally, there is a philosophical argument which tells 

 strongly for some limitations of the duration of non-sexually- 



