Hesler and Smith
Pileus: 2.5 - 8 cm broad; convex at first then planar and finally with a central or eccentric, shallow, broad depression; margins inrolled at first then decurved then undulating and eroded, even, hairy when young becoming smooth when mature; surface moist to viscid, shiny when dry, smooth, uneven to lumpy, at times with yellow brown fibrils on margins; colour pallid, white buff with some yellow tints when young darkening to brown grey at maturity; context 1 cm at junction of stipe, moist, firm, white at first then bruising to lilac purple; taste mild to slightly bitter; odour indistinct to described as sweet, fruity.
Latex: White, copious, changing to lilac purple.
Lamellae: Horizontal when young then subdecurrent to finally decurrrent, average to closely spaced, thick, narrow (0.6 cm), edges even, often bruising lilac and appearing marginate; whitish pallid at first, then yellowish white and finally pale brownish orange, spotting lilac purple from latex.
Stipe: 5 - 7 cm long X 1.0 - 2.0 cm at apex to 1.5 - 3.0 cm at base; tapering upwards to clavate; surface moist to viscid, glabrous, shiny at first then drying unpolished; colour white to pallid to buff, spotting yellow brown with lilac where bruised; context white changing to lilac when bruised, solid at first, soon hollow.
Comments: This is the only Lactarius species with white latex that turns lilac in these forests. It is usually whitish to yellow but can be darker.
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.