Echinocereus Chisoensis

Echinocereus davisii is one of many dwarf cacti of the Chihuahuan Desert in west Texas, and it has very limited distribution, restricted to a 30 mile band around Marathon in Brewster County. Plants are particularly small, at most one inch across, often mostly or entirely covered by the soil, especially during dry periods. They are found most often around outcrops of novaculite, a silaceous, flint-like rock, and associated with spike moss. In some respects, such as flower characteristics, this species is very similar to echinocereus viridiflorus, and was once considered to be a variant, but is now recognized as a separate species.

Stems have between six and nine (wavy) ribs, with areloes, on tubercles, at around a third of an inch apart. Often only a small mumber of areoles are visble, fewer than six. There are between 8 and 15 spines per areole, usually only radials, sometimes one central. Spines are white or pale gray, often brown at the tips, quite thick, and around half an inch in length. Plants usually remain unbranched.

Flowers are relatively large, up to an inch across, as wide or wider than the stem. The floral tube is spiny, and short-hairy. Tepals are pale greenish-yellow, with faint, darker, reddish midstripes. Filaments and anthers are pale yellow, the stigma lobes pale green. Fruits are brown or greenish pods, half an inch long.