2. Cassiope mertensiana (Bongard) G. Don, Gen. Hist. 3: 829. 1834.
Andromedamertensiana Bongard, Mém. Acad. Imp. Sci. St.-Pétersbourg, Sér. 6, Sci. Math. 2: 152, plate 5. 1832
Stems spreading or ascending to erect, forming dense mats, puberulent, glandular-hairy, or glabrous. Leaves imbricate, somewhat appressed to leaf above, usually 4-ranked; blade ovate-lanceolate, abaxial groove absent, 3-4.5 × 1-1.5 mm, margins thin but not scarious, without curled hairs at leaf tips, surfaces glabrous to glandular-hairy or sparsely hairy. Flowers: sepals 2-3 mm, margins entire or erose; petals connate to 1/3 their lengths, tips recurved, corolla white, campanulate, 5-8 mm; stamens to 3 mm. Capsules 1.5-4 mm.
Subspecies 4 (4 in the flora): w North America.
Four subspecies were recognized by Piper, based on differences in pubescence of the stems and leaf margins.