tical with Beijerinck's Actinococcus cya- forms of Streptomyces, whether they are neus. Beijerinck believed in a close relation- natural mutants, or whether, as Gause be- ship between his cultures and that of Strep- lieved, Streptomyces can be a mutant of tomyces coelicolor Miiller. Whether these Nocardia (Proactinomyces) , remains to be cultures are naturally occurring sterile determined. Genus II. Micromonospora Orskov, 1923. (Investigations into the Morphology of the Ray Fungi. Copenhagen, 1923, 147.) Mic.ro.mo.no'spo.ra. Gr. adj. micrus small; Gr. adj. monus single, solitary; Gr. noun spora a seed; M.L. noun spora a spore; M.L. fem.n. Micromonospora the small, single-spored (organism) . Well developed, fine, non-septate mycelium, 0.3 to 0.6 micron in diameter. Grow well into the substrate. Do not form at any time a true aerial mycelium. Multiply by means of conidia which are produced singly at the ends of special conidiophores on the surface of the substrate mycelium. Conidiophores are short and either simple, branched or clustered. Not acid-fast. Gram-positive. Strongly proteolytic and diastatic. Aerobic. Grow readily between 35° and 37° C. Usually saprophytic. Occur mostly in dust, soil and lake bottoms. The type species is Micromonospora chalcea (Foulerton) ^rskov. Key to the species of genus Micromonospora. I. Grow vigorously; copious spore formation on glucose-asparagine agar. A. Vegetative mycelium pale pink to deep orange; no typical soluble pigment. 1. Micromonospora chalcea. B. Vegetative mycelium orange, changing to brownish black; soluble pigment brown. 2. Micromonospora fusca. II. Grow slowly and feebly; scant spore formation on glucose-asparagine agar; no soluble pigment. A. Vegetative mycelium not blue. 1. Vegetative mycelium pale pink to pale orange, 3. Micromonospora parva. 2. Vegetative mycelium yellow to orange-red. 4. Micromonospora globosa. B. Vegetative mycelium blue. 5. Micromonospora coerulea. 1. Micromonospora chalcea (Fouler- black to greenish black, this color some- ton, 1905) 0rskov, 1923. (Streptothrix chalcea times spreading through the whole mass of Foulerton, Lancet, 1, 1905, 1200; Prskov, growth. Ellipsoidal or spherical conidia Thesis, Copenhagen, 1923, 156.) formed individually on relatively non- chal'ce.a. Gr. adj. chalceus copper, branching conidiophores. bronze. Gelatin: Liquefaction. Vegetative growth: Grows rapidly on all Milk: Peptonized, occasionally coagu- nutrient media, especially on glucose-as- lated. paragine agar. Growth heavy, compact. Sucrose is inverted, raised, pale pink to deep orange, not spread- Starch is hydrolyzed. ing much into the medium. Long, thin. Cellulose rapidly decomposed, branching, non-septate hyphae. Surface of Proteolytic action seems stronger in this growth smooth or folded, dull or shining. than in the other species of this genus. No soluble pigment. Nitrites produced from nitrates. Aerial mycelium: None. Well developed Aerobic, spore layer, moist and glistening, brownish Optimum temperature for growth, be-
