WILT OF CUCURBITS. 



291 



instances 2 per cent sodium chloride in peptonized bouillon inhibited growth, but in one 

 instance one tube out of five clouded thinly at the end of 12 days. The alkalinity of the 

 bouillon used for inoculation seemed to play some part, i. e., when inoculated from acid 

 bouillon (+20) even 1 per cent sodium chloride inhibited growth (cucumber strain?). The 

 organism is also sensitive to acids (fig. 95). 



Fig. 88. t 



Fig. 89.{ 



*Fig. 87. Petri-dish poured plate of B. tracheiphilus after incubating 6 days at 22 to 25 C. On Jan. 27, 1904 

 with the usual precautions against surface contaminations, a tube of bouillon was inoculated with a little white, sticky 

 slime from the interior of the inoculated cucumber-plant No. .552. Gradually the bouillon clouded thinly after the 

 manner of a pure culture and on Feb. 2, plates were poured demonstrating its purity. The largest colonies were on the 

 surface of the agar; the very small ones, in body of agar; and the thin ones, on lower surface of agar next the glass. 

 Plates made from this same tube of bouillon on Jan. 27, i.e., soon after introducing the viscid slime, remained sterile. 



fFlc. 88. Portion nf an agar-plate of B. tracheiphilus showing appearance of buried colonies, surface colonies, 

 and colonies breaking through to surface, after being incubated for 7 days at 30C. Drawn Nov. 18, 1904, from plate 1 

 Nov. 11. X2. Descended from rods which withstood freezing. 



JFig. 89. Colony of Bacillus tracheiphilus drawn by reflected light and magnified to show markings in the colony, 

 its surface being smooth. This appearance is not visible by transmitted light, nor by looking across colony at an acute 

 angle. Actual size of colony indicated by small circle. Plate I, Nov. 1 1, 1904, made from frozen bouillon and incu- 

 bated for 7 days at 30 C. 



Fig. 90. Surface growth of Bacillus tracheiphilus as seen under a low power by transmitted light, after 7 days 

 at 30 C. Colony from same agar poured-plate as fig. 89. Actual size of colony shown by small circle. Drawn Nov. 

 1 8, 1904. 



