Page:Bergey's manual of determinative bacteriology.djvu/851

 or on short lateral branches, a few to many sporangia on one hypha; they are formed in the hj^phal tufts and mounds until the latter may be almost solid masses of spor- angia. The sporangia are white in small groups, pink in large masses and spherical, measuring 7 to 19 microns in diameter on leaves, most measuring 8 to 9 microns. Shortly after their formation, spores are visible as a single coil in each sporangium; when completely formed, they are irregu- larly arranged. Immersion of the mature sporangium in water brings about the swell- ing of an intersporal substance; this swelling causes the wall and the spores to push out on one side forming a cone-shaped projec- tion about half as long as the diameter of the sporangium. The spores are forcibly ejected through an opening in the cone; they are spherical, 1.8 to 2.0 microns in diameter, possess a shiny globule and are non-motile. The sporangial wall persists for several hours after spore discharge. In addi- tion to sporangia, conidia are formed in coils somewhat as in Streptomyces, though the coils are much less conspicuous. Czapek agar: Growth fair, about 0.7 to 1.2 cm in diameter after 6 weeks; usually flat, level with agar surface; concentric zonation distinct or absent; central region usually compact with a broad fringed border and a tasseled edge. Surface glossy or pow- de^3^ Color usually white, sometimes pink- ish buff or cream-buff. Sporangia, absent to fairly abundant, are always formed some distance above the surface of the agar. In some cultures coils are formed which break up into conidia as in Streptomyces. Palisades are absent. Peptone Czapek agar: Growth good, a- bout 1.5 to 2.0 cm in diameter after 6 weeks; flat or with a few low radial or irregular ridges and grooves; margin fringed or en- tire; aerial hyphae often formed in white concentric rings, sometimes as a white bor- der and sometimes giving a powdery ap- pearance to the normally glossy surface. Olive-buff to deep olive-buff. Sporangia very rare. Potato glucose agar: Growth usually good, 1.0 to 1.8 cm in diameter after 2 months; center elevated with irregular bumps and ridges; margin flat and even with surface of agar. Color at first creamy, becoming tawny and then Carob brown or Kaiser brown, after which white floccose spots of hyphae appear, usually spreading to cover the entire culture. Sporangia are usually formed in vast numbers, the white areas becoming rosy pink as the sporangia mature; the pinkish areas are frequently minutely pocked. Surface moist at first, appearing dry and floccose as aerial hyphae and sporangia are formed. Agar colored reddish brown with a vinaceous tinge. Agar: Growth fair, 0.7 to 1.3 cm in diame- ter after 2 months; central region elevated into irregular ridges which merge, towards the outside, into radial ridges and grooves sloping abruptly to the narrow, flat border; margin lobed. Usually cream-buff, rarely buffy brown. Surface usually glossy, some- times powdery with aerial hyphae which may be united to form many upright fasci- cles. Sporangia absent. Krainsky's glucose asparagine agar: Growth poor, 0.3 to 0.7 cm in diameter; slightly elevated and minutely ridged, slop- ing to the fimbriate margin. Surface of cen- tral region minutely powdery with aerial hyphae. White. Sporangia absent. Emerson's agar: Growth good, about 2 cm in diameter after 6 weeks, composed of a whitish central area, 4 to 6 mm wide, made up of elevated, irregular bumps and ridges which abruptly change into radial ridges and grooves sloping down to a flat, white border, 1 to 2 mm wide and composed of minute, concentric circles of white hyphae. Ridges and grooves vinaceous brown, some- times covered with a whitish down. Margin smooth or scalloped, ending abruptly. Sur- face dry. Sporangia formed abundantly, appearing first in the center as the white changes to pink. Agar colored pale vina- ceous brown. Habitat: Found in vegetable garden soil, Chapel Hill, North Carolina.