50 MEDIA AND THEIR PREPARATION 
Hesse and Niedner’s (1898) Agar. 
AQAYr-AGAL. cee tweens 12.5 
Nahrstoff Heyden............. 0000000 7.5 
Distilled water... 0.0.0.0... 00. ccc cece ee eee 980.0 
Claimed to be a suitable medium for the bactcrial examination of 
water. 
Dolt’s Agar (1908). 
Purified agar (3 per cent solution)........ .... 250 ce. 
ASPAVAGIN. 2. eee ne 2 5 gms. 
NagHPOg. 2... cc ec eee 0.5 gm. 
Distilled water... 0.0.0.0... 0. c eee eee 100 c.c. 
This medium was found to support good growth of B. coli in twenty- 
four hours. 
Neutral Red Agar. Add cnough 0.5 per cent neutral red solution to 
agar containing 1 per cent dextrose to produce a clear red color. 
Corn Agar (After Barlow, 1912). 
0 6 1000 gms. 
SUCLOSC. 0... cc eee cee eee e nee eeees 80 gms. 
AQAY.. cee ene ete eens 60 gms. 
Litmus... ee eee eee 100 gms. 
Water... ccc ccc cee nents 4000 gms. 
Stir the corn into the boiling water add to other materials, boil 
five minutes, heat in an autoclave and cool slowly, the heavy matter 
settles off. The clear supernatant agar may be drawn off and tubed. 
Agar for Ps. Radicicola (Moore). 
Di-potassium phosphate ................... 1 gm. 
Magnesium sulphate.................02000- 0.5 gm. 
SUCKOSE. 2. eee eee teens 10.0 gms. 
AQar.. ccc ce eee Lecce eee eee 10.0 gms. 
Distilled water......0 20... ce cee cece eee 1000 c.c. 
Bean Agar (Thom, 1910). Common white beans are heated in 
five volumes of water. Boiling is stopped just before the swelling 
of the cotyledons would rupture the seed coats. This gives a clear 
yellow solution which filters easily and contains sufficient nutrients to 
grow many species normally. Agar may be as desired. Since this 
medium is poor in available carbon it is often desirable to add carbo- 
hydrate for certain species. 
