Summary:
Features include 1) almost bald cap that varies from reddish brown to cinnamon brown to yellow-brown to yellowish or buff, 2) dense flesh with mild taste, 3) yellow pores that usually bruise blue quickly, and 4) finely netted yellow stem.

Chemical Reactions:
flesh pale vinaceous with KOH, (Thiers, Bessette)

Odor:
not distinctive (Thiers, Bessette)

Taste:
not distinctive (Thiers, Bessette)

Microscopic:
spores (10)12-14(16) x 4-5(6) microns, subfusoid [somewhat spindle-shaped] to subcylindric [somewhat cylindric], smooth, individual spores brown in Melzer''s, amyloid in mass, pale ochraceous in KOH, thin-walled; basidia 4-spored, 26-31 x 9-12 microns, clavate, colorless; hymenial cystidia 48-65 x 8-13 microns, fusoid-ventricose, colorless, thin-walled; cap cuticle differentiated as a trichodermium of interwoven to tangled hyphae, pale brown in KOH, not incrusted; stem cuticle fertile on ridges, interwoven in other parts; clamp connections absent, (Thiers), spores 12-16 x 4-6 microns, somewhat cylindric to somewhat fusoid, smooth, ochraceous, (Bessette), spores 12-15 x 3.5-5 microns (Arora(1))

Spore Deposit:
dark olive brown (Thiers), olive brown (Bessette)

Notes:
This species has been confirmed only from CA where it occurs "in both the coastal region and in the Sierra Nevada foothills" (Arora(3)). It has been known as Boletus appendiculatus (Schaeff.) Secr. sensu Theirs. Arora(3) comment "Reports of Boletus appendiculatus sensu Thiers under conifers in the Pacific Northwest (e.g. Tylutki 1987) appear to be misidentifications based on Butyriboletus abieticola, Bu. primiregius and/or Bu. autumniregius. However, reports of Boletus appendiculatus with Q. garryana on Vancouver Island, British Columbia, are likely based on either this species and/or Bu. querciregius.", (Arora(3), with Latin names italicized). A collection from BC at the University of British Columbia as Boletus appendiculatus could be Butyriboletus persolidus or Butyriboletus querciregius.

EDIBILITY

yes, considered choice by some, but because of taxonomic confusion, use restraint, (Thiers), yes, considered choice by some, (Bessette), some people are "allergic" to it (Arora(1))

Synonyms and Alternate Names:
Boletus appendiculatus (Schaeff.) Secr. sensu Thiers California Mushrooms: A Field Guide to the Boletes: 41. 1975
Suillus cavipes (Opat.) A.H. Sm. and Thiers Contribution