tomyces, whereas, as a rule, no such mycelium is found in the isolates of Actinoplanes. As a whole, the isolates of Actinoplanes grow much more vigorously on agar than do those of Streptosporangium. The most striking difference is that in Actinoplanes the sporangiospores are motile, whereas in Streptosporangium they are non-motile. Under certain conditions of culture, some species of Actinoplanes resemble some species of Micromonospora. Indeed, a non-sporangial strain of Actinoplanes might easily be con- fused with certain micromonosporas. The spores of Micromonospora, however, are formed singly or in grape-like clusters but never in chains, whereas in Actinoplanes they are formed singly and also in chains but not in grape-like clusters. Furthermore, none of the cultures of Micromonospora so far tested forms sporangia. Another striking difference is that, with most species of Micromonospora, on certain agars, the sporulating surface turns black, whereas this change does not occur in Actinoplanes. In general, the species of Micromono- spora are less vigorous in growth than those of Actinoplanes. Several species of Actinoplanes , when grown on potato-glucose and certain other agars, will form a small, pasty culture which, when mounted and crushed under a coverslip, breaks up into minute spheres, irregular rods and short, branched, hyphal segments, much as in Nocardia. Such growth, however, is not the normal condition for any species of Actinoplanes. None of the twenty-five species of Nocardia from Baarn and from the American Type Cul- ture Collection formed sporangia when grown either on any of the agars most favorable for sporangial formation or on Paspalum leaves in water. The type species is Actinoplanes philippinensis Couch. 1. Actinoplanes philippinensis Couch, 1950. (Jour. Elisha Mitchell Scientific Soc, 66, 1950, 87.) phil.ip.pi.nen'sis. M.L. adj. philippinen- sis pertaining to the Philippines. The mycelium on sterile Paspalum grass in water forms a very delicate, hyaline to pinkish buff internal mycelium and an in- conspicuous external fringe of threads around the entire edge of the leaf; compact mounds or tufts of hyphae which are scat- tered over the top surface giving the leaf a speckled or finely powdery appearance are also sometimes formed. The hyphae are 0.5 to 1.5 microns wide, branched and sparingly septate. Sporangia are usually abundantly formed on grass after about ten days, usu- ally on long unbranched stalks; they are mostly spherical when mature and measure 8.4 to 22.0 microns, most of them being about 12.0 microns in diameter on grass. At maturity the spores are arranged in coils or are irregularly placed in the sporangium; they are about 1.0 to 1.2 microns in diameter and are discharged through a pore or by the partial dissolution of the sporangial wall, swimming vigorously. Czapek agar: Growth at room tempera- ture poor to fair, rarely good; flat or slightly elevated; sometimes in two distinct planes; one within the agar, the other at the sur- face. Margin smooth or scalloped. Light buff to tawny, changing in some old cultures to Mars brown with a lighter margin (colors as in Ridgway, Color Standards and Color Nomenclature, Washington, D. C, 1912). Sectoring frequent. In section, the growth consists of a compact surface layer, made up mostly of distinct palisades, and a sub- merged region of loosely arranged hyphae; the surface region is frequently stratose in old cultures with narrow, orange-colored layers. Sporangia are fairly abundant in some cultures and are not formed in others; they are spherical to irregular, frequently occurring beneath the surface in old cul- tures owing to overgrowth by palisade hyphae; sometimes a new layer of sporangia is formed over the first layer. Odor slightly fragrant. The agar is usually colored pale yellow. Peptone Czapek agar: Growth good to very good, consisting of heaped convolu- tions in the center, becoming concentric rings of narrow ridges with narrow radial grooves, towards the outside, usually with an elevated or radially ridged-and-grooved margin. Surface shiny. Color brilliant, near apricot-orange or orange-chrome. Sporangia absent to very rare. Palisades not formed. Smaller hyphae form vast numbers of bac- teroid spheres and rods which, when the
