Cauline leaves mostly in 5-8 pairs, blade ± ascending throughout, 0.8-1.2 mm wide. Inflorescences: branches erect to ascending. Flowers: sepals 4.5-7.2 mm, to 8 mm in fruit, ± glabrous; nectaries thickened, molarlike, apically 2-lobed, 1-1.5 mm.

Flowering spring-summer. Open woodlands, sagebrush flats, dry, rocky slopes, alluvial deposits, often on carbonates; 600-2200 m; Ariz., Calif., Nev., Utah.

Plants with petals equaling or barely exceeding the sepals and with cauline leaves fewer than five pairs have been recognized as Arenaria macradenia var. parishiorum; those features intergrade completely with var. macradenia. See M. F. Baad (1969) for his reasons for accepting var. parishiorum as a species.

B. Maguire (1947) included 'Lower California' in his distribution statement for var. macradenia, implying Baja California; we have not seen any collections from that area.

Plant: Perennial, tufted, green; stem 20-40 cm, rounded, ± dull, sometimes glandular-hairy

Leaves: simple, opposite, 20-60 mm, 0.5-2 mm wide, needle-like, herbaceous, blunt to sharp-pointed; vein 1

INFLORESCENCE: cyme, terminal; flowers several-many, compact to open; pedicels 3-55 mm

Flowers: hypanthium barely present; sepals 5, ± free, 3-7.2 mm, in fruit < 8 mm, acute to acuminate; petals 6-11 mm; nectaries 2-lobed, 0.7-1.5 mm; stamens inserted on obscure to prominent disk; ovary ± superior, styles 3, 0.5-2 mm

Fruit: Fruit: capsule, ovoid to urn-shaped; teeth 6, ascending to recurved; Seeds 4-9, 1.8-2.7 mm, ± spheric to ovate, compressed, reddish brown to blackish; tubercles low, rounded to conic

Misc: Open woodlands, sagebrush flats, dry rocky slopes; 1100-2500 m.