24 BULLETIN 1053, U. S. DEPARTMENT OF AGRICULTURE. 



Tertiary mycelium (aerial) — 



Colorless as a rule, with occasional hazel hyphse, may be slightly 

 colored in mass; 2.2 to 5.6 ji', long, stiff, hairlike; chlamydospores as 

 described in the secondary mycelium ; thick walled ; irregular hyphse 

 common. 



DIFFERENTIATION OF THE CULTURES UPON AGAR. 



Agar plate cultures of the five fungi under consideration in these 

 studies are readily distinguished macroscopically. Lenzites sepiaria 

 is readily distinguishable because of its scant superficial mycelium, 

 even occasional lack of it, and the powdery appearance due to the 

 oidia. Lenzites trabea can readily be distinguished as to its second- 

 ary mycelium by the presence of chlamydospores along with the 

 oidia, inasmuch as the chlamydospores of L. sepiaria are ver}^ 

 scarce and seldom found on malt agar. Its tertiary mycelium is 

 dense, matted, and patchy and in color yellow-orange to ochraceous 

 buff. It forms large fluffy masses at the upper ends of malt agar 

 slants. 



Of the remaining fungi here studied, Fomes roseus may show 

 only a white secondary mycelium, which will be either uniform or 

 very irregular in thickness, or there will be formed a tertiary my- 

 celium from pale-pink tints to old rose and Mars brown in color. It is 

 also a more slowly growing organism at its optimum temperature than 

 Lenzites sepiaria, L. trabea, or Trametes seHalis. Lentinus lepideus 

 grows at about the same rate as Fomes roseus, taking 12 days at 

 optimum temperature to cover a 10-centimeter Petri dish. Trametes 

 serialis is a rapidly growing fungus, covering the dish in 7 days at 

 optimum temperature. Lentinus lepideus soon .takes on a brownish 

 cast, forms umbonate abortive fruiting bodies in the Petri dishes, 

 and usually has a distinct aromatic odor. 



A conspectus of diagnostic characters of agar cultures of the 

 five fungi is presented in key form. The characters are based on 

 cultures at least 3 weeks old and grown at temperatures from 20° 

 to 30° C. 



I. Oidia present. 



A. Growth usually white, scant and powdery, but occasionally more 



abundant, and shades of brown or sepia in color, especially fruit-body 

 cultures ; true chlamydospores scarce, but many spherical or pyriform 

 oidia may be present Lenzites sepiaria. 



B. Early growth (secondary mycelium) scant and powdery, but usually con- 



taining many true chlamydospores; later growth (tertiary mycelium) 

 abundant, containing no secondary spores, pale yellow-orange to light 

 ochraceous buff in color ; abortive poroid or irpiciform fruit bodies 

 formed Lenzites trabea. 



II. No secondary spores present ; tissue cultures soon becoming pink, old rose, 



or shades of brown ; basidiospore cultures remaining white indefinitely 

 or becoming pink with age . Fomes roseus. 



