Pileus: often colored, convex to funnel shaped
Stipe: usually substantial, may be quite brittle (chalky)
Stature: Tricholomatoid, Naucorioid, Clitocyboid
Basidiospores: often globose with amyloid ornamentations
Hyphae: with sphaerocytes in the cap and stipe trama
: cheilo- and pleurocystidia present or absent (always present according to www.mycokey.com
Spore Print: white to cream
: often alternating with Lamellulae, subdecurrent to decurrent (Singer
, 1986); attached in various manners (Largent and Baroni
Lamellar Trama: subregular
Lactarius and Russula are clearly closely related and are the two members of the Russulaceae. While some microcharacters are different, in the field Russula gills tend to break cleanly when rubbed - they contain sphaerocysts), while in Lactarius they are more soft and pliant (they do not).
Of course the big difference is that Lactarius produces latex. The problem is that old specimens often do not, at which time they can be confused with Clitocybe. A quick examination of the spores will reveal if the specimen is a Lactarius.
Pay attention to the color of the latex when freshly cut, and if it turns a different color upon exposure to the air. Many keys to species are based, partly, on this character.
Lactarii are used for food in many countries in Europe, Asia and North Africa. Russians are particularly fond of pickling them.