WILT OF CUCURBITS. 265 
two next below the pricked leaf. The rest were normal. The twenty-fifth day the apical 10 inches 
including three internodes below the pricked leaf were dry-shriveled. The wilt was slowly extending 
downward. Another big leaf-blade, the fourth down, had drooped the preceding day. Farther 
down were five good leaves separated by long internodes. The stem was horizontal. The whole vine 
finally shriveled to the ground. 
(246.) Cucumber. The eighth day (10 a.m.) there was wilt of the apex and margins of the pricked 
leaf, extending outward mostly from the groups of pricks, involving 10 to 12 sq.cm. The leaf was 4 
inches broad. There had been no wilt up to the preceding afternoon, therefore the period of incuba- 
tion was nearly eight days. The tenth day the terminal three-fourths of the pricked blade had wilted 
and was a dull yellowish green (it was more green than yellow but looked faded). ‘The petiole and 
remaining leaves were normal. By January 16 the blade of the pricked leaf had shriveled. The upper 
half of the petiole was flabby and the extreme upper end was shriveling. The terminal six leaves (6 
inches of stem) had wilted and also the blade of the first leaf down, the separating internode being 4 
cm. long. The rest were normal. The twenty-first day the upper half of the vine had wilted. It was 
now brought into the laboratory and by direct transfer four slant agar-cultures were made from it 
(tubes 1 to 4, January 21, 1896) as follows: 
No. 1 from base of wilted part of stem (interior) ; 
No. 2 from interior of a young shriveling fruit 
near the top of the vine; 
No. 3 from middle of wilted part of the stem 
which had begun to shrivel; 
No. 4 from interior of stem not far from the 
lowest external sign of wilt (in leaf) and where 
the stem was sound externally but sticky within. 
Nos. 1 and 4 yielded pure cultures of Bacillus 
tracheiphilus. 
(247.) Squash. Groups of pricks were 
made on a big cotyledon. Up to March 4 
there had been no general wilt. The pricked 
cotyledon was dead and the pricked part 
was thicker than the rest as if from develop- 
ment of cork-tissue. 
(248.) Squash. One of the cotyledons 
was pricked. There was no result from 
the inoculation. Even the cotyledons did 
not wilt. There seemed to be cork in and 
around the pricked area. 
(249.) Squash. The pricks were made 
in one of the cotyledons. Up to March 4 
(63 days) there were no general signs re- 
sulting from the inoculation, although 22 
days after inoculation there was a decided 
wilt at the tip of the cotyledon which con- . ‘ 
' tinued for several days extending very Fig. 74.* 
slowly from the group of pricks outward. 
(250.) Squash. This vine was also pricked on one of the cotyledons but with no result. On 
March 4 the pricked part looked as if cork-tissue had been formed there. 
Remarks.—In the cucumbers the bacterial wilt progressed upward faster than down- 
ward, i. e., two or three times as fast. On the sixteenth day in the squash all the pricked 
cotyledons were large, thick and green. One of the pricked cotyledons wilted at the tip 
after 22 days. 
One of the cotyledons, collected March 4 (probably from 247 or 249) was afterwards 
infiltrated with paraffin and sectioned. Bacteria were present in some of the bundles and 
some of the latter were a little disorganized but not much. The impression one gets from 
these sections is that the bacteria have multiplied in the vessels very slowly. A definite 
corklayer was not made out. 
*Fic. 74.—Leaf of Cucumis sativus (plant No. 245) inoculated with B. tracheiphilus and shaded to show progress 
of wilt. The needle-pricks were made Dec. 31, 1895. First sign of disease appeared at apex of leaf on ninth day. 
About 24 hours later wilt had extended as indicated by lighter shading. Drawn by the writer. 
