640 



GERMINATION AND DORMANCY 



carbon bisulfid, xylol, ethyl bromld, and a number of other compounds were 

 also effective. Vapors of ethylene chlorhydrin so hastened the growth of 

 tubers of the Irish cobbler variety that vines two feet high bearing young 

 tubers i cm. in diameter grew from the treated tubers before the sprouts of 

 the untreated tubers appeared above the surface of the ground. Solutions 

 of sodium and potassium thiocyanate gave almost equally striking results. 

 Thiourea solutions differed somewhat from the other compounds used in that 



Fig. 141. Effect of ethylene dichlorid in breaking dormancy of lilac buds. Plant 

 on right received no treatment. Plant on left exposed 48 hours to ethylene dichlorid, 

 2.5 cc. of liquid per 100 liters of space on Dec. 10. Both plants kept in greenhouse and 

 photographed early in January. Photograph from Denny and Stanton (1928). 



they overcame the inhibiting effect of the terminal bud upon the growth of 

 lateral buds and caused the development of several shoots from each eye on 

 the tuber. 



The vapors of ethylene chlorhydrin and ethylene dichlorid also induce 

 the growth of dormant buds of lilac {Syringa vulgaris), flowering almond 

 {Primus triloba), and some other species of woody plants (Fig. 141). The 

 effect of the vapors was so restricted that when one of two paired buds of 

 a lilac was exposed to the vapor, growth occurred only in the treated bud. 

 The untreated bud remained as fully dormant as other buds more distant from 



