236 BACTERIA IN RELATION TO PLANT DISEASES. 



bug and one was on a plant bitten by the striped beetle. The latter was the only case which 

 came on with any promptness. In the others the signs appeared at such a late date that we 

 must assume the introduction of an extremely small number of the bacteria, and possibly 

 the same results would have occurred without the introduction of the squash-bugs (see notes 

 on check plant No. 22). Records later than December 10 are wanting. 



INOCULATIONS OF NOVEMBER 17, 1894. 



One well-grown tomato-plant and 6 young squash-plants which were large for their 

 age were pricked with a steel needle at 3 p. m., and inoculated with Bacillus tracheiphilus 

 (cucumber-strain). Nothing could be more vigorous or apparently more disease-resisting 

 than these young squash-vines. They were growing in 3-inch pots in the hothouse at the 

 time of inoculation. 



(41.) Tomato (Lycopersicum esculentum). A plant about 12 inches high, healthy and growing 

 rapidly, was pricked on several leaflets of 3 leaves. Into one set of pricks I put bacteria taken from 

 a potato-broth-culture of November 15. This was derived from slant potato-culture No. i, Novem- 

 ber 12, which was made from slant potato-culture No. 8, October 17, already found by previous inoc- 

 lations to be virulent (see Nos. 34, etc.). The second leaf received very sticky, actively motile bacteria 

 direct from tube i November 12. The third leaf was inoculated with bacteria taken from a slant 

 agar-culture (No. 12, October 28) which was from No. i, October 23. This agar-culture was alive 

 the preceding day as determined by its motility. The ninth day there was no wilt. The vine was 

 growing rapidly and was exceedingly vigorous. It was now re-inoculated on 3 end leaflets of one of 

 the leaves, from a colony (in the tube used for inoculations of November 26) in which more than half 

 of the bacilli were actively motile, darting about in the water with great rapidity. The nineteenth 

 day no signs had appeared. On this day (December 6) the vine was inoculated a third time, the 

 part selected being a stout branch on the upper part of the stem, one which grew from the axil of the 

 leaf pricked the ninth day. About 30 pricks were made, the needle being dipped into the culture each 

 time. Sometimes the needle was thrust entirely through the stem. The culture used was a potato- 

 broth (tube 2, December 3) in which the bacilli were motile. The twenty-third day this vine was 

 making a magnificent growth. It had been inoculated three times but was pricked again on this date. 

 The pricks, which were very numerous and which carried into the plant great numbers of sticky motile 

 bacteria derived from potato-culture No. 5, December 6, were made on the main stem toward the top 

 over a distance of 4 to 5 inches both in the internode and the two nodes (which were less woody). 

 A fifth inoculation was made January 3, using a great quantity of motile living bacteria taken prob- 

 ably from the slant agar culture of December 28. The needle was touched to the culture each time 

 before using and 50 punctures were made. 



On January 26, this tomato-plant into which I had pricked hundreds of thousands of living rods 

 of B. tracheiphilus at various times during 2 months preceding, had made a strong growth and was 

 entirely free from the wilt. It had outgrown the pot and the whole top was now cut away preparatory 

 to repotting. The inoculation of January 3, like the others, caused no disease. The most that could 

 be seen externally on January 26 was a slight shrinking and change of color to a duller green around 

 the pricks, as if the bacteria had perhaps grown out into the tissue for a slight distance. The pricks 

 themselves had enlarged with the increase in length and diameter of the stem and were bordered by a 

 narrow ring of dry, dead tissue. Owing to growth of the plant the pricks were now about as long 

 again as broad and, including the border of dead cells, most of them measured 1X0.5 mm. The leaves 

 near these pricks had remained healthy and the upper one had sent out a shoot from its axil since the 

 inoculation. This shoot was 12 cm. long, and healthy. Beginning with the node out of which this 

 shoot grew, and extending down 2 cm. there were 1 7 needle-punctures, all on the same side as the shoot 

 and the nearest one within 4 mm. of its base. There was no evidence of any rot or softening around 

 the pricked place externally or internally and a microscopic examination of unstained free-hand 

 sections showed no bacilli in the tissues around the punctures. The branch into which the bacteria 

 were pricked had shown no sign of disease and there was no change of color in the living tissue around 

 the punctures, which were narrowly bordered by a band of white dead cells. This branch was pre- 

 served in alcohol. On March 12, there was still no trace of wilt. 



(42.) Hubbard Squash (Cucurbita sp.). This vine, which showed the second true leaf, was 

 infected near the tip and in the middle of one of the green cotyledons. Many pricks were made using 

 a white, sticky, wet-shining bacillus from slant potato-culture No. i, November 12 (cucumber-strain). 

 The eighth day the cotyledon was yellowing in the pricked middle portion but without wilt. The 

 next morning the yellowed area had increased in size. The tip seemed a little flabby but the wilt 



