2l8 BACTERIA IN RELATION TO PLANT DISEASES. 



(4.) August 30, a young squash-fruit was punctured in 40 places and many germs thrust in 

 from several of the white colony-like bacterial beads on cut stems. The fruit oozed juice profusely. 

 September 6: Squash still sound externally. On making sections through the flesh it looks water- 

 soaked around the stabs for a breadth of nearly a millimeter. It is not rotten. Placed in moist air 

 under a dish there is a moist sticky ooze from these water-soaked parts; not white; no ooze from 

 other parts. 



(5.) September i : A leaf 7 inches across was wet on the upper surface over a square inch and a 

 large white bacterial bead from the cut stem stirred up and pricked in with a needle. The leaf was 

 then doubled together and inserted in a glass fruit jar (moist inside) and left 24 hours, the mouth 

 being plugged with damp cotton wool (a defective method). September 2: Removed. No result 

 where the germs were pricked in, but a sun-burn has appeared on the other half of the leaf. Septem- 

 ber 11, 10 a. m. : Two small wilted spots have appeared on the area which was pricked ten days ago; 

 6 p. m. : Spots have enlarged, each being about three-quarters of an inch long (each side of a vein) 

 and not over one-fourth inch wide. The petiole of this leaf is 6 inches long and all leaves on the axis 

 above and below are healthy. 



(6.) September i : A vigorous terminal shoot was enclosed in a large glass jar (wet inside and 

 plugged with damp cotton wool), two leaves 3 or 4 inches wide, being first wet and several white 

 masses of the bacterial ooze stirred into the water and then pricked in with a needle. September 2 : 

 Both infected leaves have blighted one-third to two-thirds and three others which touched them 

 also show it. The blight includes the veins. These leaves are much younger and tenderer than in 

 Experiment 5 (all probably due to sun-burn). September 1 1 : Solely sun-burn. 



(7.) Two ends of a vigorous squash vine were put into a wet glass can, two leaves on each being 

 infected with bacteria brought from Washington. This growth was wrinkled, dirty Isabella color 

 [the wrong organism]. The bacteria were teased up in water on the leaf and pricked in with a needle ; 

 two more were infected in the same way from another block of potato in the same Petri dish. Mouth 

 of can was closed with cotton and wet rags. All 4 leaves blighted in 24 hours, but probably all was 

 due to sun-burn. September 1 1 : Solely sun-burn. No colonies appeared on cut ends of stem or 

 petioles which were yellowing. 



(8.) Some germs from the potato cultures [wrinkled dirty organism] were inserted into 2 green 

 tomatoes and into the stem very thoroughly with needles. September 1 1 : Tomatoes rotted slowly. 

 Stem turned dark around puncture i mm. or more on outside and germs evidently infiltrated some 

 distance into the tissue. My father afterwards picked and threw away the tomatoes for rotted, not 

 knowing that I had inoculated them. 



(9.) Germs from the very gelatinous Isabella-colored, wrinkled, colony [wrong organism] on 

 potato were rubbed up in well-water and pricked into the parenchyma and veins of four large turgid 

 squash leaves, both sides, pretty thoroughly, with a cambric needle on September 7, 1 1 a. m. 

 Leaves several feet from ends, and marked with twine. No results. 



(10.) September 7 : The two turgid leaves (two different vines) which had bacteria pricked into 

 them August 30, from the white ooze on cut squash-stems (see No. 3) are now badly wilted, while all 

 the leaves to either side are turgid. These leaves are about 18 inches from the growing ends of the 

 vines. I first detected the wilt yesterday morning (September 6), i. e., about 8 days after the infection. 

 They looked all right for 5 or 6 days and I had abandoned the experiments as hopeless and did not 

 look at them for 2 days. The wilt to-day (September 7, 1 1 a..m.) is very decided and I can attribute 

 it to nothing but the slow growth of the inserted germs. I now know all of the other supposed 

 infections (i. e., those obtained in moist air in 24 hours inside of glass jars) to be due in great part at 

 least, and probably altogether, to sun scald. This was determined by getting the same results 

 without use of germs. The cans rested on hot sand and the air became very hot inside and was 

 saturated or nearly so with vapor of water.* September 10 : The two squash leaves wilted completely 

 but slowly, and are now crisp dry. The petioles are still green and turgid, but one seems a trifle flaccid 

 at the extreme tip although not yet shrunken or discolored. This one was cut away and divided into 

 o.75-inch segments, and put on end in moist air. Two hours later there were plain indications of 

 bacterial ooze from the cut bundles on some of the segments, and at 6 p. m., i. e., in 7 hours, all of the 

 segments had each several beautifully distinct milk white bacterial beads resembling colonies. This 

 was true even of the segments cut 3 or 4 inches below the blade of the leaf. This sets at rest all 

 doubt regarding the possibility of inducing the disease by pricking in the bacteria taken fresh from 

 the cut stems. September 1 1, 6 p. m. : Leaves to each side of these two are still perfectly healthy and 

 no similar case of natural wilt at end of vines has appeared on any of the vines during the time I 

 have been here. There is no shadow of doubt now as to what caused these leaves to blight. The 

 striking thing is [was to me at that time] that the blight should have taken 8 days to develop. Only 



'Defective technique. 



