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

Figs. 27-38: fig. 27, pleurocystidium of Tylopilus umbrosus; fig. 28, spores
of same; figs. 29-30, spores of T. nebulosus; fig. 31, spores of Suillus americanus;
figs. 32 and 35, spores of T. sordidus; fig. 33, cheilocystidia of same; fig. 34,
pleurocystidia of Suillus americanus; fig. 36, pleurocystidia of T. sordidus; fig. 37,
spores of T. pseudoscaber; fig. 38, cheilocystidia of T. pseudoscaber.