METHODS OF BREAKING THE DORMANCY OF BUDS 639 



year at which the vapor is applied. In late summer or early fall several 

 weeks may elapse between the exposure to ether vapor and the active growth 

 of the buds. Late in the winter, however, the interval is shortened to a day 

 or two. 



Fig. 140. Breaking dormancy of buds of blueberry by low temperatures. The 

 branch on the right was exposed to low temperatures by allowing it to project through 

 a small hole in a greenhouse during the winter. The branch on the left remained 

 within the greenhouse. Figure shows appearance of plants on Apr. 18. Photograph 

 from Coville (1920). 



More recently a number of other chemical treatments have been discovered 

 that are successful in breaking the dormancy of buds. Denny (1926) found 

 that dormant potato tubers sprouted freely when exposed to ethylene chlor- 

 hydrin vapor. Sodium and potassium thiocyanate, thiourea, dichloroethylene. 



