124 CKOWN-GALL OF PLANTS. 



The remaining 11 covers were dropped into 6 tubes of bouillon at 

 the end of 20 days but no growth ensued (28 days). The character 

 of gro^\i;h of the daisy organism in beef bouillon renders it difficult to 

 get an even, tliin cUstribution and proper drying on cover slips, and to 

 tliis is probably attributable the fact that the organism was ahve on 

 3 of the 25 covers after the first day. 



Tliis experiment was repeated in June, 1910 (temperature 30° C), 

 using a peptone bouillon culture 5 days old and tliinner smears, the 

 covers being kept in the dark, with the follo\\^ng result : 



Test begun at end of 2 days — 



(1) Two days, 2 tubes — no gi-owth. 



(2) Tliree days, 1 tube — no growth. 



(3) Seven days, 16 tubes — no growth. 



The 16 tubes were under observation for 13 days. 



A second repetition in July, 1910 (temperature 30° C), using a 

 6-day-old peptone bouillon culture, the covers being kept in the dark, 

 gave the follomng results: 



Test begun first day — 



(1) One day, 2 tubes — both grew, one very slowly. 



(2) Two days, 1 tube — no growth. 



(3) Three days, 1 tube — no growth. 



(4) Five days, 1 tube — no growth. 



(5) Six days, 1 tube — no gi'owth. 



(6) Nine days, 1 tube — no growth. 



(7) Ten days, 1 tube — no growth. 



(8) Twelve days, 18 tubes — no growth. 

 The last lot was under observation for 10 days. 



EFFECT OF SUNLIGHT. 



Organism moderately sensitive to sunlight. — Agar tubes of the daisy 

 organism inoculated from 3-day bouillon cultures were poured into 

 Petri dishes and placed in the bright sunlight for 45 and 60 minutes, 

 half of each plate being covered \^'ith black paper. After 4 days on 

 each of the four plates there were numerous colonies under the covered 

 parts, but none on the exposed parts. On 8 plates exposed at this 

 time for shorter periods (30, 15, 10, and 5 minutes) colonies appeared 

 on the exposed parts, but they were fewer than those on the shaded 

 parts. Results similar to those just detailed were obtained by a 

 repetition at 30 minutes. Colonies came up slower on the exposed 

 side of the plate, but finally there were many. A second repetition 

 gave similar results at 30 and 35 minutes. In a repetition at 35, 40, 

 and 45 minutes, made a few weeks later (experiment begun April 3 in 

 bright sunlight and final examination made April 11) tiny colonies 

 appeared the third day on the sliaded side of all the plates, but none 

 at all developed on the exposed side (8 days). 



213 



