204 R. M. SAMISH 



the number, and about four times this number of buds sprouted 

 after the maximum chilling period. 



In warm countries, insufficiency of chilling prolongs rest, 

 delaying bloom and fruit maturation, and reducing the number 

 of buds which open. Thus, both the photosynthetic area and the 

 number of blossoms are affected. These phenomena, together 

 with certain additional physiological disturbances caused by 

 prolonged rest, constitute a serious economic factor with the 

 result that certain crops cannot be grown economically in 

 regions with warm winters. 



Horticulturists — as in our department — try to solve this 

 problem by methods such as selecting and breeding varieties 

 with low chilling requirements. The artificial breaking of rest 

 represents an additional possibility. Johannsen- was the first to 

 do so by means of anaesthesia. Molisch^ interrupted the rest 

 period by immersing plants in a warm water bath. The physio- 

 logical mechanism of this treatment was explained by Boresch'^ 

 on the basis of anaerobiosis. For trees, we studied a number of 

 sprays, the effects of which are described in Table III. On the 



TABLE III 



THE EFFECT OF MINERAL OILS AND CERTAIN DINITRO-COMPOUNDS ON THE 



AWAKENING OF DELICIOUS APPLE BUDS 



* U.M.R. = unsulphonatable residue = % saturated constituents. 



** Dinitrocompounds = concentrations equimolecular to dinitrocresol, 



1.5 % in the mineral oil. 



