46 BACTERIA IN RELATION TO PLANT DISEASES. 



February 14. Johnston's plates miscarried (probably too thinly sown). Miss Hedges then 

 poured plates from Johnston's second bouillon dilution, which had been saved and was now moder- 

 ately clouded, and got Bacterium vascularum in pure culture. Probably by far the larger part of the 

 bacteria in this stem were dead, as in case of canes Nos. 30 and 36. 



February 19, 1906. The plates poured January 13 from inoculated plant No. 63 (Cinta) showed 

 nothing for quite a number of days, so that we thought they had been inoculated too thinly. After- 

 wards numerous yellow colonies came up, but it required a week or more. 



General Remark. When I finished cutting out the cane on February 9 a stalk of Crys- 

 talina was selected which showed yellow ooze from some bundles, and dark purple-red ooze 

 from others. Two sets of plates were poured: one from the red ooze, one from the yellow 

 ooze. Just as in the previous set of plates there was for a number of days no indication 

 of colonies, but afterwards the plates showed numerous typical colonies of Bacterium vascu- 

 larum. The plates poured from the red ooze showed no red colonies, but only yellow ones. 



This indicates two things: First, that the dark red ooze was due not to red-colored 

 bacteria, but to a red reaction of the host plant; and, second, that when the bacteria have 

 lain dormant for many months in old canes they are not resuscitated as early as from fresh 

 growths. The same remark applies to other bacteria causing plant diseases. 



The results from this series of inoculations indicates also very clearly that it is difficult 

 to obtain secondary (stem) infections on old canes by means of leaf -inoculation unless such 

 canes have grown rapidly. The primary signs on these plants were entirely satisfactory, 

 the constitutional ones so scanty that I had great reason to be thankful that it was not my 

 first series of inoculations. As it was, the experiment proved more instructive than if it 

 had been an exact duplicate of the first one. 



SERIES VII, 1906. 



On February 9, 1906, thirty-five young green shoots (second growth) were inoculated 

 with Bacterium vascularum by means of hypodermic injections. To each of the slant agar 

 cultures (1 to 3, February 7, descended from three separate colonies on Mr. Johnston's 

 plate 2, January 13, poured from artificially infected sugar-cane No. 63) 10 c.c. of autoclaved 

 redistilled water were added. The tubes were shaken until most of the pale yellow slime 

 was washed off and this milky fluid was injected into the plants in 2 to 4 c.c. quantities. 



Most of the inoculations were made in or above the heart (2 to 4 pricks in each plant), 

 but some of each variety were pricked in the leaves only with 6 to 8 pricks. The varieties 

 inoculated were as follows: 



106-110, Caledonia Queen, pricked in stem; m-112, Caledonia Queen, leaves pricked. 



1 1 3-1 15, Louisiana No. 74, stem pricked; n 6-1 17, Louisiana No. 74, leaves pricked. 



1 1 8-1 19, Common Green, stem pricked; 120, Common Green, leaves pricked. 



1 21-123, Jamaica, stem pricked; 124, Jamaica, leaves pricked. 



125, Striped Green, stem pricked; 126, Striped Green, leaves pricked. 



127-133, Crystalina, stem pricked; 134-135, Crystalina, leaves pricked. 



136-138, Jamaica, stem pricked; 139, Jamaica, leaves pricked. 



140, Common Green, stem pricked. 



Local signs appeared on some of these plants within a few weeks, but constitutional 

 ones never developed, at least not so as to be conspicuous, and the plants after making a tall 

 growth and standing for 18 months were finally cut down to make room for other things, 

 without being examined internally. 



GENERAL REMARKS ON THE INOCULATIONS. 



In all, 140 canes have been inoculated in the greenhouses in Washington, 26 with 

 Bad. vast ularum, plated from the Australian cane, the remainder (except as noted under 

 Series V) with descendants of this strain isolated from stem-bundles of the artificially 

 infected plants at long distances from the point of inoculation (3 to 5 feet). The results 

 have varied according to the variety and the condition of the plants at the time of 

 inoculation. Canes, even of sensitive varieties, which had grown very slowly or were old 

 and woody at the time of inoculation, were not susceptible to general infection. 



