Pileus 5-12 cm broad, convex, expanding to almost plane; surface viscid, polished when dry; margin entire, inrolled when young; color white when young, golden brown in age with bister brown on the base of a slant; context very soft, pallid yellow, unchanging when injured or bruised; taste and odor not distinctive. Tubes 7-14 mm deep, at first adnate to depressed around the stipe but soon decurrent, yellowish pallid when young, becoming yellow, unchanging when injured; pores pale yellow becoming yellow, 1-2 per mm, glandular dots, often with pinkish droplets of exudate when young. Stipe 6-14 cm long, 9-18 mm thick, attenuated upwards, solid, becoming hollow and soft, surface white with vinaceous to pinkish glandular dots and smears, but ground color yellow in age and the glandular areas discoloring to gray on drying; no veil present at any stage. Spore print dull cinnamon. Spores 16-19 × 5.5-6.5 μm, inequilateral in profile, oblong in face view, smooth, hyaline to melleous in KOH, mostly pale yellow to nearly hyaline in Melzer's reagent. Basidia 43-50 × 14.5-19 μm, subcylindric to subclavate, thin-walled, 4-spored, sterigmata 4-5 μm long, hyaline in KOH, slightly yellowish in Melzer's. Pleurocystidia 45-70 × 5-9 μm, subcylindric to narrowly clavate, scattered, typically in fascicles, hyaline in KOH, often with bister content and dark brown amorphous pigment masses incrusting the bundle at the level of the hymenium, pale yellow in Melzer's reagent. Caulocystidia 20-40 × 6-18 μm, mostly sphaeropedunculate or capitate, often with long narrow pedicels, thin-walled, hyaline in KOH. Pileal cuticle a viscid or gelatinous pellicle, composed of hyaline to pallid brown hyphae (with gelatinizing walls), hyphae 8-19 μm wide, often a more compact layer of gelatinizing hyphae immediately under the gelatinous epicutis, no clamps observed.
Specimens：
Taiwan, Nantou: Hui-Sun Forest Experimental Station, alt. 1850m, 15 Aug. 2001, Chen CM. 3032 .
Habitat：
Solitary under Pinus morrisonicola Hay. forest.
Distribution：
Taiwan, Japan, North America, China (Sichuan, Tibet, Guizhow, Yunnan).
References：
Gilbert, EJ. 1931; Singer, R. 1945ab; Chen, CM et al. 2002.
Provided：
C. M. Chen
Note：
Gilbert (1931) reviewed the boletes, and grouped the two closely related species, I. placidus (Bonorden) Gilbert and I. leptopus (Pers.)Gilbert ( = Suillus granulatus (L. ex Fr. Kuntze ssp. leptopus (Pers.)Sing.), under the genus Ixocomus ( = Suillus). I. placidus has a white-lemon pileus and an elongated stipe, and occurs under the pine tress Pinus strobus and P. cembra, whereas I. leptopus has a short stipe and its habitat is associated with Mediterranean pines. Also, spores of I. placidus are longer than 8 um, whereas those of I. leptopus are less than 8 um. Singer (1945a) recognized I. placidus as a distinctive species and placed it under the genus Suillus. Later Singer (1945b) considered I. placidus an exannulate form of S. acidus (Perk)Sing. S. placidus is fairly similar to S. acidus in many aspects, particularly the characters of the pileus. However, these two species are distinguishable in the field. S. placidus has a long, exannulate and "ㄑ" shape stipe, which is longer than the diameter of pileus, and has slime on pileus that becomes gray to black with age. S. acidus has a long, annulate but straight stipe, and slime on pileus is yellow in color.
Phylum：Basidiomycota >> Class： Basidiomycetes >> Order： Boletales 
BCRC Number：