XIX.] PEACH TREES AND COLD. 325 



offspring over its general weakness would be true 

 acclimatization. Variation in constitution is well 

 illustrated by the peach. It is well known that 

 dormant fruit buds and the trees themselves are killed 

 at a much higher temperature in the southern states 

 than in the northern states. Twenty degrees below 

 zero does not often kill mature peach trees in Michi- 

 gan ; but in southern Illinois, as Parker Earle writes 

 me, they are usually killed by a temperature of ten 

 to fifteen degrees below zero. 



Mr. Crozier* records testimony to the effect that 

 peach trees in Michigan were injured no more at a 

 temperature of twenty degrees below zero than they 

 were in central Mississippi at a temperature of zero. 

 Peach buds are injured at a much higher temperature 

 at the south than at the north. Mr. P. H. Mell, 

 Jr., director of the Alabama Polytechnic Institute at 

 Auburn, writes me that buds are often killed even at 

 a temperature of thirty -four to thirty -eight degrees 

 above zero. This observation undoubtedly refers to 

 the partially expanded buds, yet it is well known 

 that at the north a considerable frost is required to 

 kill the swelling buds. It is possible that all these 

 instances of the peach should fall under the division 

 of adaptation through modification of individual con- 

 stitution ; but as I cannot be certain, if indeed it is 

 probable, that all these cases represent bud offspring, 

 I place the statements here. If trees of the same 

 variety show this difference in different latitudes, as 

 they undoubtedly often do, then we have indispu- 

 table evidence of the acclimatizing of the individual. 



It is well known that seedlings grown in the 



• Modification of Plants by Climate, 21. 



