272 



BACTERIA IN RELATION TO PLANT DISEASES. 



petiole being still rigid. Two days later the plant was very sick, all of the leaves, seven in number, 

 having wilted. The eleventh day the stem was still green and turgid. July 14 the plant was entirely 

 dry-shriveled as a result of the inoculation. 



(295.) Cucurbita foetidissima (Tourney's first sending to Mr. Hicks). The sixth day (3 p.m.) 

 there was no sign of the disease but 23 hours later the leaf on the pricked side had changed to a dull 

 green and was wilted over an area of about 10 sq. cm. from the pricks outward, up, down, and inward 

 to the midrib. The rest of the plant was uninjured. The ninth day the whole of the pricked leaf 

 had shriveled except the petiole which was turgid. For distribution of the bacteria in the petiole 

 of such a leaf see fig. 77, and for a detail from the same see fig. 78. The wilt now also showed on the 



blades of three other leaves — the first 

 down and the first two up. Two days 

 later all but one leaf was wilted, the 

 stem, however, was still turgid and 

 green. On July 14 the plant was dry- 

 shriveled, with the exception of the 

 base of the stem which was green. 



(296.) Apodantheraundulata(pTOTn 

 Toumey, Tucson, Arizona). The 

 pricked leaf was examined frequently 

 but there was no marked result from 

 the inoculation. On July 14 the plant 

 was healthy. Part of the pricked area 

 had dried out and most of the leaf- 

 blade which was pricked was yellowish 

 and yellow-green, but it had never 

 shown any tendency to wilt. 



(297.) Apodanthera undulata. The 

 seventh day all the foliage was slowly 

 drying out but not as a result of the 

 inoculation. Two days later there was 

 a slight wilt (3X4 mm.) in the center 

 of the pricked part. This portion later 

 became dried out and brown but the 

 plant did not contract the disease and 

 on July 14 the rest of the pricked leaf 

 was normal. 



(2g8.) Apodanthera undulata. Plant 

 examined June 23, 25, 27, and July 3. 

 There was no result from the inoculation. 

 Up to July 14 the pricked leaf had not 

 wilted and the plant was healthy. 



(299.) Cucurbita palmata? (Seeds 

 received from Toumey: Said to have 

 been collected in California). Up to 

 July 14 there had been no wilt and the 

 plant was growing rapidly. 



(300.) Cucurbita palmata (?). On 

 June 25 the plant was normal. The 

 eleventh day the pricked blade was yellow 

 and shriveling, but 28 days after the inoc- 

 ulation there was still no general wilt. 

 (301.) Cucurbita palmata (?). Up to June 27 the pricked leaf showed no signs. On July 14 the 

 pricked leaf-blade had wilted and some of those above it were yellow, but it was doubtful whether 

 this was due to the disease because there was a fine growth of healthy vine beyond the pricked leaf 

 and no good leaves below it. 



(302.) Cucurbita digitata (From Toumey. The plant identified as Cucurbita calif ornica looks 

 and tastes something like this). The seventh day there were tiny dead spots in the pricked area 



*PiG. 77. — Cross-section of leaf-stalk of Cucurbita foetidissima, the wild gourd of the western plains of the United 

 States, showing vascular system occupied by Bacillus tracheiphilus. Plant grown in a hothouse in Washington from 

 seeds obtained in Arizona. Inoculation from a pure culture by means of needle-pricks in blade of leaf. Petiole fixed 

 in strong alcohol, infiltrated in paraffin, sectioned on microtome, stained in carbol-fuchsin, and differentiated in 50 

 per cent alcohol. Drawn from section with aid of Abbe camera. Slide 254 D i . 



Fig. 77.* 



