6 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN NO. 21 



ated the so-called "warm water bath" as a forcing agent and found 

 radium emanations to be effective for breaking the rest period. 

 Jesenko 1 caused earlier growth in woody twigs by immersing them 

 in weak alcohol. He obtained similar results by treatments with 

 weak solutions of hydrochloric and tartaric acids. Weber 2 demon- 

 strated that mechanical.. injury induces resting buds to begin growth. 

 Lakon 3 claimed to have secured earlier bud development by using 

 nutrient salt solutions. Ethyl bromide and other vapors were used 

 by McCallum. 4 Harshberger 5 found that resting buds which were 

 treated with NH 4 OH grew before untreated buds. Bos 6 used the 

 galvanic current as a means of arousing plants from their dormancy. 

 Placing plants in a vacuum, according to Stuart 7 was an effective 

 means of breaking the rest period. Bathing the twigs in plant 

 extracts, CuSO 4 , KC1, NaNO 3 , oxalic and acetic acid dilutions have 

 induced somewhat earlier growth of buds. Similar results were 

 obtained by painting the twigs with MnO2. (See page 45). 



The value of agents and methods for breaking the rest period 

 varies with the species and other factors, such as time and intensity 

 of application, condition of the twig, etc. Some agents are more 

 effective than others. In general, the intensity of all treatments, 

 that is, the concentration of the liquids, the density of the vapors, 

 the duration of application or the degree of heat, etc., must be de- 

 creased as the season advances and as the close of the rest period is 

 approached. Applications which are very effective in December may 

 be very injurious during March. 



RESUME OF THEORIES REGARDING THE INFLUENCE OF 

 REST PERIOD BREAKING AGENTS 



The miscellaneous materials that have been successfully used 

 in breaking the rest period have given rise to much speculation as 



1. Jesenko, Fr., Einige neue Verfahren die Ruheperiode der Holzgewachse 

 abzukurzen. Ber. d. d. Bot. Ges. (1911) 29, p. 273. 



2. Weber, F., Untersuchungen Ueber die Wandlungen des Starke und 

 Fettegehaltes der Pflanzen insbesondere der Baume. Bot. Centrlb. 113 (1910) 

 p. 166. 



3. Lakon, G., Influence of Nutrient Solutions on the Winter Rest of Woody 

 Plants. Ztsch. f. Bot. 4, pp. 561-83. 



4. McCallum, W. B., On Forcing Plants. Arizona Sta. Report, 1909, pp. 

 584-86. 



5. Harshberger, J. W., Action of Chemical Solutions on Bud Development: 

 An Experimental Study of Acclimatization. Proc. Acad. Sc. Phil. 61, pp. 57-110. 



6. Bos, H., Wirkung galvanischer Strome auf Pflanzen in der Ruhperiode. 

 Biolog. Zentrabl. (1907) 27, No. 2. 



7. Stuart, W., The Role of Anesthetics and other Agents in Plant Forcing. 

 Vermont Sta. Bui. 150, pp. 451-480; also Trans. Mass. Hort. Soc. 1909, pp. 67-87. 



