672 



SCIENCE 



[N. S. Vol. XXV. No. 643 



fact that galk closely resembling the young 

 stages of crown-gall have been produced on the 

 roots of peach trees by needle-pricks, intro- 

 ducing this organism. In eighteen days these 

 growths have reached the size of small peas, 

 the checks remaining unaffected. It is too 

 early, perhaps, to say positively that the cause 

 of the wide-spread and destructive crown-gall 

 of the peach has been determined by these 

 inoculations, but it looks that way. Of 

 course, the most that can be affirmed abso- 

 lutely at this writing is that we have found 

 an organism which when inoculated into the 

 peach produces with great regularity galls 

 which in early stages of their growth can 

 not be distinguished from the crown-galL 

 The matured daisy galls also look astonish- 

 ingly like the peach gall. Numerous experi- 

 ments which ought to settle the matter defi- 

 nitely in course of the next three months are 

 now under way. In the best series of experi- 

 ments on peach roots (that inoculated from 

 a standard nutrient agar culture five days old") 

 14 groups of needle-punctures (5 in each 

 group) were made on nine trees, 13 timiors 

 resulting. The fourteenth group was on a 

 weak tree which did not leaf out, and might 

 therefore be left out of the count. In that 

 case we have 100 -peT cent, of infections. On 

 the roots of nine young trees from the same 

 lot, held as checks, Y5 punctures were made, 

 using a sterile needle, but no galls resulted. 

 In another series of 9 peach trees inoculated 

 at the same time as the preceding and. ex- 

 amined on the twenty-third day, Y5 per cent, 

 of the punctures had yielded galls (9 tumors 

 on 7 plants). These roots were inoculated by 

 needle-pricks from a culture believed to be 

 rather too old (glycerin agar streak 6 days), 

 but the plants were set out again, and it 

 is not unlikely that galls will finally de- 

 velop on the roots of the other two plants. 

 The plants, inoculated and uninoculated, were 

 set, immediately after making the needle- 

 punctures, in good greenhouse soil, in new 

 ten-inch pots, and have been subject to the 

 same conditions as to light, heat and water. 



That crown-gall of the peach is due to a 

 myxomycete the writers have never been will- 

 ing to admit, because the inoculation experi- 



ments described by Professor Tourney do not 

 clearly establish such fact. He saw often in 

 the tissues of the galls what he interpreted 

 to be the protoplasm of a slime mold mixed 

 in with the protoplasm of the host plant, and 

 he obtained sparingly what he supposed to be 

 the fruiting bodies of this organism on the 

 cut surface of the galls. He made, however, 

 only two series of inoculations with the spores 

 of his Dendrophagus gloiosus, four trees in 

 the first ease and six trees in the second, ona 

 developing the disease in the first instance 

 and two in the second. Why did not the 

 other seven trees contract the disease when 

 the spores were thrust into the wounded 

 tissue? He did not fully exclude the possi- 

 bility that the three infections were due to 

 some other cause accidentally introduced on 

 his needle point. The Dendrophagiis spo- 

 rangia furnishing spores for the inoculations 

 grew not on culture media but on the cut sur- 

 face of a gall (an infectious substance). 

 What if a few bacteria had been carried up 

 from the surface of the gall, contaminating 

 the surface or interior of the sporangia? 

 Then the needle might occasionally have in- 

 troduced two organisms into the wounds in- 

 stead of one, as believed, and the unsuspected 

 one might have been the cause of the disease. 

 This supposition is not excluded by any of 

 Professor Toumey's experiments. 



The fact remains well established, however, 

 by experiments of various persons: Thaxter, 

 Halsted, Selby, Tourney, Smith, Von Schrenk 

 and Hedgcock, etc., that when minced galls 

 are buried in the earth near the roots of sound 

 trees, the latter develop galls. The disease is 

 therefore a communicable one, but the cause, 

 in spite of much study by many persons, is 

 still in dispute. 



For the organism causing these tumors the 

 name Bacterium tumefaciens is proposed with 

 the following brief characterization : B. tume- 

 faciens n. sp., a schizomycete causing rapid 

 multiplication of the young tissues of Chry- 

 santhemum frutescens, Prunus persica, etc., 

 the result being the production of tumors or 

 galls. The organism is motile, especially in 

 young cultures; it is non-gas-forming and 

 aerobic (twelve days) with all of the sugars 



