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

BOLETUS

361

true trichodermium), cells tubular, elongate, content ochraceous in KOH,
darker yellow-brown in Melzer's but giving to the naked eye a bluish
black color to the layer, subcutis not colored distinctively in Melzer's.
Clamp connections none.
Habit, habitat, and distribution. -Gregarious in beech-maple and in
oak forests, common during warm wet weather in the summer.
Observations.-The Michigan material is not quite typical of the
species. The olive FeS04 reaction and the rare (as far as observed)
pleurocystidia are diverging features. Further studies are desirable now
that the species with setiform caulocystidia can be readily excluded.
Subsection BOLETI
The tubes are stuffed when young, the stipe is reticulate at least in
the upper third, and the flesh is typically white to pallid when fresh.
The basidiocarps are robust and fleshy and blue stains are known for
only one of our taxa. Some of the best of all edible fungi are found in
this group, but for the most part the species are sporadic in appearance
in the state or abundant from year to year only in certain localities,
such as around Marquette.
KEY TO SPECIES
1. Spores 13-17 x 4-5.5 (17-25 x 6.5-12) p (the large spores with walls
1-2 p thick); tubes bright yellow young, brownish yellow mature........................................ B. gertrudiae
1. Spores and tubes not as above............................ 2
2. Pileus cuticle more or less a palisade of large end-cells and pileocystidia, the latter often with secondarily formed cross walls........ 2
2. Pileus cuticle a trichodermium or of appressed hyphae........... 4
3. Pores staining bluish when injured........ B. separans var. subcaerulescens
3. Pores not staining blue................... B. separans var. separans
4. Pileus lemon-yellow splashed ferrugineous to vinaceous-tawny; pores
staining vinaceous-cinnamon when bruised.......... B. chippewaensis
4. Not as above.................................... 5
5. Spores 12-15 x 3.8-4.5,; content of trichodermial hyphae reddish in
Melzer's; clamp connections occasional onhyphae of the basidiocarp.. B. insuetus
5. Not as above-spores typically longer and wider.................. 6
6. Pileus viscid or slightly viscid when fresh and moist...B. edulis and variants
6. Pileus dry and unpolished when fresh..................... 7
7. Trichodermial hyphae roughened as in Leccinum insigne (fig. 15)... B. atkinsoni
7. Trichodermial hyphae smooth............................. 8