The boletes of Michigan, by Alexander H. Smith and Harry D. Thiers.

BOLETUS

293

Habit, habitat, and distribution.-Scattered on barren soil, Berry
Creek Woods, Wolverine, July 28, 1961, Smith 63736.
Observations.-A collection of this species from a wet aspen log
was made July 15, 1968, at the University of Michigan Biological Station, Cheboygan County. In it the spores measure 9-12 X 4-5 u and are
truncate. The stipe was rhubarb-red in the cortex, and this color was
evident near the base on the surface. The surface of the stipe was
pruinose-scabrous on the order of a species of Leccinum with moderately fine ornamentation. The small spores of this species at once distinguish it from B. truncatus, but there are in addition other differences
such as lack of red or purple in the cracks in the pileus, at least in
material observed to date, and the olivaceous-pallid stipe apex when
young as contrasted to yellow. Singer, Snell, and Dick described the
spores of Xerocomus truncatus as 12-17 (26) X (4.2) 4.5-6.5 /, but
Coker and Beers for their B. chrysenteron gave the spores as 3.8-5 X
9.5-12.5 g, the size which distinguishes B. subdepauperatus from B.
truncatus.
Section PIPERATI (Singer), comb. nov.
Ixocomus sect. Piperati Singer
Rev. de Mycol. 3:38. 1938
For the distinguishing characters see the key to sections.
Type species: Boletus piperatus.
KEY TO SPECIES
1. Hymenophore almost lamellate.......... see a variant under B. piperatus
1. Hymenophore definitely tubulose, pores small to large.............. 2
2. Pores staining blue if injured................... B. piperatoides
2. Not changing to blue anywhere if injured................... 3
3. Taste m ild........................................ 4
3. Taste peppery to acrid................................. 6
4. Spores 12-15 A long; pileus subtomentose and red....... B. rubinellus
4. Not with above combination of features.................... 5
5. Spores bright olive to olive-yellow in KOH; pleurocystidia absent to rare
and inconspicuous......................... B. pseudorubinellus
5. Spores hyaline to dingy yellowish in KOH; pleurocystidia scattered to
abundant................................. B. rubritubifera
6. Taste sharply acrid; pores mostly 1-2 per mm.......... B. piperatus
6. Taste merely peppery; pores in age 2-3 mm wide......... B. amarellus