Hesler and Smith
Pileus: 1.5 - 7.0 cm broad; convex when young, sometimes with an acute umbo then planar to depressed at maturity; margins straight and even, surface dry to viscid, polished, smooth at times pruinose towards disc; when young, orange to deep reddish brown on disc, fading to reddish orange towards the margin, becoming paler when mature becoming reddish orange on disc and light orange on margin; context thin, firm, light orange; taste mild becoming bitter not peppery, odour indistinct.
Latex: White colour unchanging, mild, at times turning gills reddish brown.
Stipe: 1.5 - 2.0 cm long X 0.3 - 0.7 cm wide at apex, 0.5 - 1.0 cm at base; tapering upwards to equal, surface dry to moist, polished, firm at first then fragile; light orange brown, at times mottled with beige pallid colours; context solid at first, then hollow, colour paler than stipe surface, pale to light orange.
Comments: This species and its relatives are often found on coarse woody debris. There are at least 5 different species with the stature and appearance of L. luculentus var. laetus in these forests. These species are differentiated by the taste, which can be peppery, latex colour, that may change from white to yellow, and by the type of cuticle of the pileus. To reliably differentiate similar species from L. luculentus var. laetus detailed microscopic characteristics are required.
Hesler, L.R. and A.H. Smith. 1979. North American species of Lactarius. Univ. Michigan Press. Ann Arbor, Mich. pp 841.
Methven, A.S. 1997. The Agaricales (gilled fungi) of California. 10. Russulaceae II. Lactarius. Mad River Press. Eureka Ca. pp 78.