Crown-Gall of Apple and Peach 19 



Moisture relation. — On February 24, 1914, tests were instituted to 

 determine the vitality of B. tumefaciens in dry, moist, and saturated 

 clay, loam, and quartz. Sterilized material in test tubes was used, and 

 the tubes were constantly covered with a bell glass to prevent evaporation. 

 On March 11, 1914, the organism was alive in all nine tubes. On April 10, 

 1914, the three tubes of dry material were tested and the organism was 

 recovered. In a duplicate set' of tubes which were not covered, the 

 organism was dead on the latter date in the dry clay and the dry quartz. 

 All the protected tubes were tested on November 18, 1914, and B. turner 

 faeiens was found to be alive except in the tubes of dry clay and dry quartz. 

 Sterilized wheat seeds were planted in some of the tubes of moist loam on 

 April 17. The seeds grew and developed into plantlets. On May 29 a 

 test was made of these tubes and B. tumefaciens was found to be alive. 



Penetration of soil. — Tubes were filled with moistened quartz and with 

 moist loam, and were sterilized. Five cubic centimeters of a culture 

 of B. tumefaciens was poured into one end of each tube, and enough 

 sterilized water was added so that water would drip from the other end. 

 This was caught under aseptic conditions, and at the end of forty-eight 

 hours was tested by plating. The organism was recovered from tubes 

 60 centimeters in length. No greater lengths were tested, as 60 centi- 

 meters represents the approximate penetration into the soil of roots of 

 young trees. Similar tests with clay gave penetration in some instances 

 and not in others. Apparently, if the clay became "puddled" from 

 adding water too rapidly, the organism was filtered out. 



While these tests are not extensive, they certainly indicate that, when 

 free from competition, B. tumefaciens can live for several months in moist 

 soil of various types, that it can withstand low temperatures and repeated 

 change in temperature at or near the freezing point, and that it may move 

 considerable distances with currents of soil water. 



Memoir 67, Observations on the Life History of Taphrocerus gracilis (Say) (Beetle, Family Buprestidac), 

 the sixth preceding number in this series of publications, was mailed on September 14, 1923. 



