Pomona College Journal op Economic Botany. 



331 



heated in the steam, sterilizer for one hour, and sterilized for thirty min- 

 utes on three successive days. 



Nutrient agar (M3.) This medium consisted of the following materials: 



Thread agar was soaked in tap water Por thirty minutes, washed in dis- 

 tilled water and boiled in nearly the full amount of water until thoroughly 

 dissolved. The other ingredients were then added, the whole made up to 

 250 c. c. with distilled water, filtered through absorbent cotton, and steri- 

 lized for twenty minutes on three successive days. 



Nutrient agar (M4). This medium consisted of the same materials 

 as (M3), prepared in the same manner except 1.25 grams of dextrose was 

 used in place of 1.25 grams of beef extract. 



Prune juice and bread (M5). Seventy grams of dried prunes were 

 washed carefully in tap water, rinsed in distilled water and cooked slowly 

 in distilled water until the prunes M'ere thoroughly softened. The fleshy 

 part of the prunes was mashed into a pulp, enough distilled water added 

 to bring the total up to 500 c. c, strained through a clean towel and the 

 liquid filtered through absorbent cotton. About 25 c. c. of this liquid was 

 put into each 200 c. c. flask and sufficient bread crumbs added to soak up 

 the liquid. The flasks were sterilized for twenty minutes on three succes- 

 sive days. 



Steamed white corn meal (M6). Ten grams of meal and 35 c. c. of 

 distilled water were used for each 200 c. c. flask. This medium was steri- 

 lized for thirty minutes on three successive days. 



Steamed rice (M7). Ten grams of rice and 40 c. c. of distilled water 

 were used for each 200 e. c. flask. This medium was sterilized for thirty 

 minutes on three successive days. 



Steamed potato plugs (IMS). Large, sound potatoes were thoroughly 

 scrubbed, washed and cut into cylinders about 1 inches long and one-half 

 inch in diameter with a large cork borer. These cylinders were cut length- 

 wise diagonally, thus each cylinder made two plugs with slant surfaces. 

 These plugs were washed in running water twelve hours, rinsed twice in 

 distilled water and sterilized for twenty minutes on three successive days. 



Ratv potato plugs (M9). These plugs were prepared in the same man- 

 ner as the steamed plug.s, except they were washed in 4% fonnalin solution, 

 rinsed several times in distilled water and not sterilized. 



Steamed beet plugs (MIO). A large, sound beet wa.s thoroughly 

 scrubbed, washed and prepared in the same manner as the steamed potato 

 plugs, but not washed in running water. 



Agar-agar 

 Peptone 



.1.2%— 3 grams 

 1.0% — 2.5 grams 

 .0.5%— 1.25 grams 

 0.5%— 1.25 grams 

 .250 c. c. 



Salt 



Beef extract .... 

 Distilled water 



