28 



Research Bulletin No. g 



suggested by Hasselbring (14) was followed. Erlenmeyer flasks 

 of 200 cc. capacity were used with 50 cc. of solution per flask. The 

 solutions in the flasks were autoclaved for 10 minutes at 7 lb. 

 pressure, and then inoculated by means of sterile pipettes with a 

 drop or two of spore suspension. The cultures were killed by 

 adding 10 cc. of 10 per cent HC1 to each flask. The cultures 

 were then filtered off on tared Gooch crucibles prepared with 

 asbestos, washed until acid free, and brought to constant weight in 

 a Freas electric oven at ioo° C, and the dry weight determined. 

 It was found impossible at times to filter luxuriant cultures of 

 F. oxysporum by this method, because of the tenacity with which 

 this organism holds water. Consequently they were filtered on 

 soft filter paper, transferred to tared Gooch crucibles, dried, and 

 weighed. The other organism holds water with little tenacity and 

 filters with ease. 



In all of experiments given below the following stock mineral 

 solution was used: 20 gm. NH 4 N0 3 ; 10 gm. KH 2 P0 4 ; 5 gm. 

 MgS0 4 per 1000 cc. H 2 0. When carbohydrates were employed, 



Dry weight (in milligrams) after 20 days' growth in potato extract medium; 

 ROOM temperature 



*For 20 days (no growth), then at 25° C. for 25 days. 



