No. 601] RESISTANCE OF PRUNUS TO CROWN GALL 



49 



tible hosts were always included in the experiment, to act as a 

 check upon the virulence of the culture and any unfavorable 

 climatic condition. In each series of inoculation 5 or 10 punc- 

 tures were made upon vigorous growing twigs of the current 



year's growth. During the experiments of 1914, ten punctures 

 were always made. This number, being the same in all the ex- 

 periments, was of material aid in the final compilation of results. 

 Other check punctures were made in the same way as in the in- 

 oculations except that none of the organisms were placed in the 

 tissue. An ordinary steel needle in a cedar handle was used in 

 making the puncture inoculations. This was first flamed, then 

 used to convey some of the bacterial growth from the test tube 

 to the twig to be inoculated, the puncture being made through the 

 bark and wood of twig. The organism was grown in a medium 

 made as follows : ^ per cent, glucose, ^ per cent, sodium chloride, 

 i per cent, meat extract, 1 per cent, peptone, 1 per cent. agar. 



