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 /x; 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 trdbea 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 very 
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 semalis. 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. 
