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

BOLETUS

251

smooth as revived in KOH, in Melzer's with fine hyaline granules adhering to distal portion, content yellow in KOH in fresh material, hyaline
as revived, content not distinctive in Melzer's.
Tube trama parallel but- slightly divergent near the subhymenium.
Pileus cutis a tangled trichodermium the elements of which are 5-10/L
wide, a fair number of the cells short and these often disarticulating,
walls thin and smooth, cell content yellowish to hyaline in KOH, in
Melzer's the layer rusty brown from patches of incrusting material adhering variously to the cells back from the terminal cell (similar to the
material in the cuticle of B. spadiceus). Hyphae of the context not
distinctive in either KOH or Melzer's. Clamp connections absent.
Habit, habitat, and distribution.-Gregarious among poison ivy
under oak, Washtenaw County, September, rare. It seems to fruit in the
early fall if the weather is exceptionally wet.
Observations.-The outstanding features of this species are its
poroid hymenophore, conspicuously reticulate stipe, the tenacious hold
it has on the substratum, and the rusty brown incrustations on the cells
toward the base of the trichodermial hyphae as revived in Melzer's. This
material is somewhat dextrinoid.
Subsection SUBTOMENTOSI
This grouping features species that stain blue slightly on the pores
when bruised, but see also B. minutiporus of the previous subsection in
which the context stains slightly bluish. The pores typically are angular
at maturity, and the pileus is velvety when young. Singer (1965) has, in
our estimation, given a good account of this group, one of the most
puzzling of the boletes, and we have adopted his treatment with such
new features added as the hyphal incrustations, as seen in mounts revived in Melzer's, and the amyloid reactions.
KEY TO SPECIES
1. Cuticular hyphae (elements of the pileus trichodermium) with bister walls
in Melzer's and some incrustations present in KOH mounts, the incrustations dark yellow-brown in KOH; pileus surface brownish when
NH40H is applied directly to fresh material......................................... (see B. subparvulus also) B. chrysenteron
1. Not with above combination of characters..................... 2
2. NH40H on pileus giving a fleeting green to blue-green reaction............................ (see B. minutiporus also) B. spadiceus
2. NH40H giving a brown to mahogany-red reaction.............. 3