FAMILY IV. ACTIXOPLANACEAE 



827 



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 



