INTRODUCTION

Considerably more field work must be done before a comprehensive key can be written for Hebeloma in the Pacific Northwest. It has been said in jest that there are only four species: veiled Hebeloma, poison pie (Hebeloma crustuliniforme), scaly-stalked Hebeloma (Hebeloma sinapizans group), and sweet-smelling Hebeloma (Hebeloma sacchariolens). That is just to illustrate the difficulty of distinguishing members of the genus which David Arora calls “another faceless and featureless collection of brownish mushrooms”.

A monograph for the veiled Hebelomas was written by A.H. Smith et al. in 1983, The veiled species of Hebeloma in the western United States. The monograph describes more than 90 species of which about a third had collections examined from the Pacific Northwest. Most of the rest were described from Colorado and could occur in the Pacific Northwest. The monograph has now been made available by the University of Michigan online at
http://quod.lib.umich.edu/cgi/t/text/text-idx?c=fung1tc;cc=fung1tc;view=toc;idno=AAW6632.0001.001
The keys it contains should be consulted for detailed work. They have been abstracted below to contain only the species that Smith et al. document from the Pacific Northwest, in this case defined as British Columbia, Washington, Oregon, and Idaho. Identification is based on microscopic features.

Three other uncommon veil-less species are considered here under Subgenus Denudata. One of these, Hebeloma spoliatum, has been studied by Naohika Sagara and found to fruit only through the application of ammonia or ammonia-releasing nitrogenous material (such as rotting carcasses) to soil, thus it is among those Hebeloma species that could be a "corpse finder".

Descriptions of the veiled species are found in the monograph mentioned above. Hebeloma crustuliniforme, Hebeloma sacchariolens, and the Hebeloma sinapizans group are well described by Arora (1986). Hebeloma spoliatum is described in Smith(1938) and Smith (1984), Hebeloma arenosum by Burdsall et al.(1986), and Hebeloma avellaneum in Kauffman & Smith (1933) and Smith & Weber (1979).

Hebeloma crustuliniforme Kit Scates Barnhart

Hebeloma mesophaeum group Kit Scates Barnhart

Hebeloma sacchariolens Kit Scates Barnhart

Hebeloma sinapizans group Paul Kroeger

KEY TO SPECIES

1a Veil present, usually fibrillose to cortinate (Subgenus Hebeloma)

................................................................................2

1b Veil absent (Subgenus Denudata)

................................................................................501

2a Spores in profile view bean-shaped to elliptic or ovate, the apex +/- rounded (Section Mesophaea)

................................................................................3

2b Spores +/- inequilateral in profile and narrowed to a blunt apex or apex +/- snoutlike (Section Hebeloma)

................................................................................4

3a Spores 10-15 um long or longer (Subsection Subviscidae)

................................................................................101

3b Spores 7-10 (11) um long (Subsection Mesophaeae)

................................................................................201

4a (2b) Pileus white to pallid or cream color (Subsection Pallidae)

................................................................................Hebeloma salmonense

4b Pileus more highly colored when young than in above choice

................................................................................5

5a When fresh the odor fragrant to pungent-aromatic (Subsection Praeolidae)

................................................................................Hebeloma praeolidum

5b Not as above (the odor if present +/- pungent to radishlike)

................................................................................6

6a Spores 7-10(11) um long (Subsection Mesosporae)

................................................................................301

6b Spores (9) 10-15 um or longer (Subsection Magnisporae)

................................................................................401

101a (3a) Odor and taste of radish, lamellae pinkish gray, veil pallid

................................................................................Hebeloma vinaceogriseum

101b Odor and taste not distinctive

................................................................................102

102a Odor and taste farinaceous, interior of stipe bay-red

................................................................................Hebeloma sterlingii

102b Odor and taste not distinctive, stipe not splitting lengthwise, gregarious not caespitose

................................................................................Hebeloma ollaliense

201a (3b) Cuticle of pileus an ixotrichodermium rarely collapsing to an ixolattice (study young pilei) (Stirps Pseudostrophosum)

................................................................................202

201b Not as above (cuticle rarely an ixolattice in age)

................................................................................203

202a Cheilocystidia 40-70 x 7-12 x 2.3-5 um

................................................................................Hebeloma pseudostrophosum

202b Cheilocystidia 28-43 x 5-7 x 7-9 um

................................................................................Hebeloma alpinicola

203a (201b) Pileus and/or gills staining dark brown to blackish on some basidiocarps in situ (Stirps Nigromaculatum)

................................................................................204

203b Not staining as above

................................................................................205

204a Veil whitish (pallid)

................................................................................Hebeloma nigromaculatum

204b Veil (or at least outer layer) buff to pale tan

................................................................................Hebeloma angelesiense

205a (203b) Stipe not darkening at base in age (Stirps Pascuense)

................................................................................Hebeloma perigoense

205b Stipe soon darkening in basal area at least (Stirps Mesophaeum)

................................................................................206

206a Odor and/or taste raphanoid

................................................................................207

206b Odor and/or taste not as above

................................................................................Hebeloma mesophaeum

207a Spores 7-9 x 4.5-5.5 um, veil copious

................................................................................Hebeloma strophosum var. strophosum

207b Spores 8-11 x 5-6 um

................................................................................208

208a Veil copious and remains long persistent on margin of pileus and/or stipe

................................................................................Hebeloma strophosum var. occidentale

208b Veil thin and scarcely leaving a zone of fibrils on the stipe

................................................................................Hebeloma mesophaeum

301a (6a) Stipe not darkening in lower part by maturity

................................................................................302

301b Stipe darkening (often slowly) from the base upward

................................................................................304

302a Taste bitter-farinaceous; pileus orange-brown when moist

................................................................................Hebeloma aurantiellum

302b Not as above

................................................................................303

303a Cheilocystidia 26-33 x 8-12 um

................................................................................Hebeloma immutabile

303b Cheilocystidia 40-67 x 4.5-7 um

................................................................................See Hebeloma fastibile

304a (301b) Spores 7-9 x 4-5 um

................................................................................Hebeloma olympianum

304b Spores larger

................................................................................305

305a Odor fragrant; cheilocystidia 27-41 x 8-11 um

................................................................................Hebeloma pinetorum

305b Not as above

................................................................................306

306a Cheilocystidia 18-26 x 3-4 um, many of them tibiiform

................................................................................Hebeloma subhepaticum

306b Cheilocystidia not as above (at least wider than 3-4 um)

................................................................................Hebeloma parcivelum

401a (6b) Stipe not staining or discoloring in the lower portion by late maturity (Stirps Coniferarum)

................................................................................402

401b Stipe soon darkening at base or lower portion, then upward

................................................................................404

402a Cheilocystidia fusoid-ventricose, the apices subcapitate; odor pungent

................................................................................Hebeloma pungens

402b Not as above

................................................................................403

403a Cheilocystidia (some of them) cylindric-subcapitate; pileus slimy viscid

................................................................................Hebeloma kelloggense

403b Not as above

................................................................................Hebeloma pseudofastibile

404a (401b) Spores dextrinoid (medium to dark reddish brown in Melzer’s (Stirps Kuehneri)

................................................................................405

404b Spores not dextrinoid, but in a mount a few may be found which become pale to +/- reddish brown in 30 minutes; (dried specimens are most reliable for this test) (Strips Oregonense)

................................................................................408

405a Spores 9-12 um long

................................................................................406

405b Spores 10-15 um or more long

................................................................................Hebeloma marginatulum

406a Odor and taste mild or odor weakly pungent

................................................................................407

406b Odor and taste raphanoid

................................................................................Hebeloma pseudofastibile

407a Veil whitish

................................................................................Hebeloma occidentale

407b Veil grayish

................................................................................Hebeloma obscurum

408a (404b) Taste and usually the odor of the crushed context raphanoid

................................................................................409

408b Not as above (odor +/- pungent in some and in others the taste farinaceous to bitter or at least not raphanoid)

................................................................................413

409a Spores 9-12 um long

................................................................................410

409b Spores (10) 12-15 um long

................................................................................412

410a Spores 9-12 x 5-6.5 um

................................................................................Hebeloma fastibile

410b Cheilocystidia not as above (at least wider than 3-4 um)

................................................................................411

411a Veil remnants on stem white

................................................................................Hebeloma latisporum

411b Veil remnants pale ochraceous

................................................................................Hebeloma idahoense

412a (409b) Spores distinctly rough under a high-dry objective

................................................................................Hebeloma stanleyense

412b Spores appearing smooth under a high-dry objective or a 1.25 NA objective

................................................................................Hebeloma oregonense

413a (408b) Stipe staining yellow where injured

................................................................................Hebeloma lutescentipes

413b Stipe not staining yellow where handled

................................................................................Hebeloma oregonense

501a Spores 9-12 um long

................................................................................Hebeloma sacchariolens

501b Spores (10) 12-15 um long

................................................................................502

502a Spores 9-12 x 5-6.5 um

................................................................................Hebeloma sinapizans group

502b Cheilocystidia not as above (at least wider than 3-4 um)

................................................................................503

503a Spores 9-12 um long

................................................................................Hebeloma crustuliniforme

503b Spores (10) 12-15 um long

................................................................................504

504a Spores 9-12 x 5-6.5 um

................................................................................Hebeloma avellaneum

504b Cheilocystidia not as above (at least wider than 3-4 um)

................................................................................505

505a Spores 9-12 um long

................................................................................Hebeloma arenosum

505b Spores (10) 12-15 um long

................................................................................506

506a Spores 9-12 x 5-6.5 um

................................................................................Hebeloma spoliatum

506b Cheilocystidia not as above (at least wider than 3-4 um)

................................................................................many other undocumented or undescribed species

REFERENCES

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