110 CEOWN-GALL OP PLANTS. 



along the line of the streak, which is slightly elevated with entire 

 margin. It spreads rapidly and in from one to two days covers the 

 entire surface of the cylinder. The white growth has a smooth sur- 

 face with a wet-glistening appearance. It has a slimy to viscid con- 

 sistency, is free from odor, and turns the potato cylinder a grayish 

 color, which becomes darker with age. It is never yellow on potato. 

 The organism has but little action on the potato starch and its 

 growth on potato is correspondingly transient. 



STARCH JELLY. "^ 



Growth scanty; diastasic action absent or feeble; medium unstained 

 or only slightly stained. Some years later the experiment was re- 

 peated and continued for a longer time with the same result, except 

 that the old daisy strain, which had become noninfectious, now 

 stained the medium brown. 



NUTRIENT GELATIN.^ 



Colonies. — Colonies dense, wliite, circular, small, nonliqucfying. In 

 plates poured March 26 from a 3-day-old bouillon culture carried to 

 a second dilution the colonies w^ere numerous, but remained very 

 small. The surface colonies were 1 to 1.5 mm. at the end of 4 days 

 at 20° C. and were not larger 2 days later (Brown). In thinly sown 

 plates the growth of the surface colonies was slow, the largest being 

 2 mm. in diameter at the end of 24 days at 16° C; they were round, 

 white, dense, flat to raised, with entire edge, and no sign of liquefac- 

 tion (Smith) . They were never yellow with fringed margins. 



Streaks. — There is a very good growth, starting of slowly at a tem- 

 perature of 11° C. on gelatin streak cultures. 



This experiment was repeated two years later, using gelatin from 

 another laboratory with identical results. The gelatin was +12 on 

 Fuller's scale. The temperature varied from 9° to 10° C. There was 

 very slight growth up to the end of the third day. At the end of 12 

 days there was a good white growth. 



At room temperatures (22° to 23° C.) on the same gelatin at the 

 end of 2 days the streaks were as good as streaks of the same age on 

 + 15 peptonized beef agar, but this parallel growth did not continue. 

 At the end of 4 days the agar streaks showed a copious growth, while 

 the gelatin streaks showed only a moderate growth. At the end of 

 13 days the gelatin streaks were pure wiiite, wet-shining, smooth on 

 the surface, with bunches (tufts) of small cr3^stals projecting from the 

 under surface of the streaks into the unstained gelatin. Some white 

 slime had also run down into the V. There was no liquefaction. 



o For composition, see "Bacteria in Relation to Plant Diseases," vol. 1. 



6 Peptonized beef bouillon with 10 per cent Nelson's photographic gelatin No. 1 and made +10 on Fuller's 

 scale with sodium hydroxid. 



213 



