Jtinei, I9SO 



Decline of Pseudomonas ciiri in the Soil 



217 



already noted in the behavior of the dry soil series when no control was 

 exercised over the rate of drying. In a preliminary test, comparisons 

 were made of the infective power of soil samples similarly inoculated 

 and air-dried with different rates of rapidity at approximately the same 

 rather warm temperature. A sample dried in less than one day gave 1.5 

 per cent infection, one dried in two days gave o.i per cent infection, and 

 one dried in seven days gave no infection in tests made in each case 

 immediately after drying. 



An extended test of persistence in air-dry soil was made by Miss Clara 

 H. Hasse. On October 22, 1918, soil from Winter Park, Fla., was heav- 

 ily inoculated and dried as quickly as possible, in about one hour. Tests 

 for infectiveness were made by several methods, usually by dusting the 

 dry soil over punctured leaves which were atomized with water, the 

 plants being later held in moist chambers. The total punctures inocu- 

 lated in each test ranged from 600 to 5,000. The following percentage 

 results were obtained: 



On December 22, 1919, a portion of this soil was moistened with tap 

 water from a deep well and was tested on the fourth and seventh days 

 in comparison with the part remaining dry. In these tests the moist- 

 ened soil gave no infection, while the dry soil continued to show traces. 



PERSISTENCE IN SOILS MADE ARTIFICIALLY ALKALINE AND ACID 



Greenhouse potting soil was used in 6-inch pots. Duplicate pots were 

 watered each with 400 cc. of water containing 1.6 cc. sulphuric acid. 

 Two pots were watered with 400 cc. of water containing 224 cc. clear 

 lime water prepared by slaking 25 gm.. quicklime and making up to 1,000 

 cc. A titration test showed this lime water to be sufficient to neutralize 

 the quantity of acid applied to the other pots. A third pair of pots was 

 watered with 400 cc. distilled water. After Standing three days all pots 

 were equally inoculated with P. ciiri. On each sampling date litmus paper 

 tests of the i/i soil washings were made, and such small amounts of lime 

 water or diluted acid were added as seemed necessary to maintain 

 approximately the original distinct acidity in one set and distinct 

 alkalinity in the other. The watering of all sets was equalized. The 

 percentage results given in Table IX are based on infections out of 2,000 

 inoculated punctures. 



