fla.ves'cens. L. part. adj. flavescens be- coming gold-colored. On media where a firm growth is produced, the vegetative mycelium appears as long, branched, non-septate hyphae, 0.4 to 0.6 micron in diameter. In other media, as on nutrient agar and potato, septa are formed, and the mycelium appears in preparations as fragments of very variable size, partly resembling highly branched mycobacteria. In several cases — for instance on nutrient agar at 28° to 30° C, in 5 to 6 weeks-old cultures in glucose broth and in glucose NH4CI solution — short elements assume swollen, fusiform to lemon -shaped forms. The aerial mycelium consists of fairly long hyphae of the same diameter as the vegeta- tive hyphae, not very much branched, without spirals, often clinging together in wisps. A differentiation into spores is never visible b.y direct microscopic e.xamination. Neither is this the case in stained prepara- tions: here the aerial hyphae break up into fragments of quite variable length, from 1.2 to 1.5 up to 10 to 12 microns, showing an irregular, granulated staining. Gelatin: Slow liquefaction. Sucrose agar: Good growth. Vegetative mycelium superficially spreading, much raised and wrinkled, cracking, white to cream-colored, of a dry, but loose and crumbly, consistency. Aerial mycelium scant, thin, white. Faint yellow, soluble pigment after 2 to 3 weeks. Glucose agar: Good growth. Vegetative mycelium superficial, wrinkled, honey-yel- low, of a hard and cartilaginous consistency. Aerial mycelium thin, smooth, white. Yel- low, soluble pigment. Nutrient agar: Good growth. Vegetative mycelium raised and much wrinkled, first dirty cream-colored, later dark yellowish gray, of a soft, moist, curd-like consistency. No aerial mycelium. No pigment. Glucose broth: Rather scant growth. Granulated, yellowish sediment; no sur- face growth. Broth clear. No pigment. No acidity. Milk: Coagulated and slowly redissolved with acid reaction. Potato: Good to excellent growth. Vege- tative mycelium much raised and wrinkled, first cream-colored, later yellowish brown, soft and smeary. No aerial mycelium; no pigment. Sucrose is inverted. Starch is hydrolyzed. Cellulose not decomposed. Nitrates are reduced slightly or not at all with various sources of energy. Final reaction in glucose-NH4Cl solution, pH 3.9 to 3.6. No growth under anaerobic conditions. Source: Isolated from soil. Habitat: Soil. 35. Nocardia gibsonii (Erikson, 1935) Waksman, 1953. {Ac.tinornijces gibsonii Erik- son, Med. Res. Council Spec. Rept. Ser. 203, 1935, 36; Streptomijces gibsonii Waksman and Henrici, in Manual, 6th ed., 1948, 963; Waksman, in Waksman and Lechevalier, Actinomycetes and Their Antibiotics, Balti- more, 1953, 155.) gib.so'ni.i. M.L. gen. noun gibsonii of Gibson; named for Prof. Gibson of Oxford. Young, growing mycelium branches pro- fusely at short intervals; later grows out into long, frequently wavy filaments; twisted hyphae also seen on water agar. Power of producing aerial mycelium ap- parently lost. Gelatin: Dull white flakes sinking as the medium liquefies; liquefaction complete in 12 days. Agar: Small, cream-colored, depressed, partly confluent colonies, becoming an ex- tensive, wrinkled, cream-colored skin. Glucose agar: Cream-colored, wrinkled, membranous growth. Potato agar: Wrinkled, glistening, mem- branous growth. Serum agar: Small, moist, cream-colored colonies growing into medium. Dorset's egg medium: Small, round, smooth, colorless colonies with conically elevated centers. Inspissated serum: Innumerable color- less, pinpoint colonies with scant white aerial mycelium at top; after 8 days, a coherent wrinkled skin with brownish red discoloration at reverse, medium becoming transparent; completely liquefied, pig- mented brown in 15 days. Blood agar: Yellowish, confluent bands.
