A. Gray—Do varieties wear out, or tend to wear out? 118 
their force since. Weeping willows, bread-fruits, bananas, 
sugar-cane, tiger-lilies, Jerusalem artichokes, and the like, have 
been propagated for a long while in this way, without evident 
decadence. 
Moreover, the analogy upon which his hypothesis is founded 
will not hold. Whether or not one adopts the present writer's 
merease. It looks odd enough to see a writer like Mr. Sisley 
reproducing the old hypothesis in so bare a form as this: “TI 
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, 
~ ho one in his senses will dispute.” Now what people in 
eir 
other trees, established from cuttings of it, will die with it. 
hon that are possessed by varieties and species propagated sex- 
tally~i. 6, by seed? Those who think so jump too soon at 
With potato 
such + 
creased liability or diminished resistance to sich attucks? And 
. you say that, anyhow, such varieties do not die of old age— 
ne that each individual attacked does not die of old age, 
es manifest disease—it may be asked in return, what indi- 
; Some limitations of the 
AM. Jour, 8er.—Tarnn Serres, Vou. IX, No. 50.—Fes., 1875. 
8 
