Loss of Moisture from Winter Twigs. 



11 



in a living-room, where the readings could be 

 taken at frequent intervals. It will be noticed 

 that the rate of evaporation was nearly constant, 

 averaging about one -half a centigram per hour: 



It has been said that the rate of the loss of 

 moisture from trees in winter determines the rela- 

 tive hardiness of different varieties of apples, and 

 of some other fruits ; and similar inferences have 

 been made respecting the ability of foliage to endure 

 summer droughts. The following table shows studies 

 of twigs of varieties of different degrees of hardi- 

 ness, but it will be seen that the per cent of loss 

 of moisture bears no relation to the supposed 

 hardiness of the varieties. 



Early in April, twigs from the previous year's 

 growth were taken from several varieties of apples, 

 which vary much in their ability to endure our cli- 

 mate (those marked by asterisks being supposed to 

 be the hardiest varieties). The twigs were carefully 

 weighed, and the cut ends were then sealed with 

 wax to prevent evaporation only through the bark. 

 At the expiration of two days the wax was re- 

 moved and the twigs were again weighed. The 

 twigs were kept in an open shed: 



