These forms have been variously referred to Anhalonium and Echinocactus, but seem to deserve generic distinction. They differ from Anhalonium in the entire suppression of the upper highly differentiated portion of the tubercle, in the broad and rounded development of the lower portion, and in the coalescence of the enlarged tubercles into broad vertical ribs. In fact, in young specimens, the plant appears almost smooth, with shallow furrows radiating from the depressed apex. The genus differs from Echinocactus in the suppression of the spine-bearing areolae, and the naked ovary. In the examination of developing tubercles the relation to Anhalonium is evident. In the latter genus the young tubercle bears on the summit of its pedicel-like lower portion the tufted flower-bearing areola the modified upper portion of the tubercle at that time appearing as a bract beneath the flower. In Lophophora there is the same condition of things, except that the bract-like upper portion is wanting. From this point of view it would appear that the differences between Lophophora and Echinocactus are intensified by the fact that the flower-bearing areola in the former genus is to be regarded as really lateral on a tubercle the upper part of which has disappeared. This genus occurs abundantly in southeastern Texas, extending southward into Mexico. Mrs. A. B. Nickels reports that the Indians use the plants in manufacturing an intoxicating drink, also for "breaking fevers," and that the tops cut off and dried are called "mescal b.u.t.tons."

1. Lophophora williamsii (Lem).

Echinocactus williamsii Lem. Allg. Gart. Zeit. xiii. 385 (1845).

Anhalonium williamsii Lem. in Forst Handb. Cact. i. 233 (1846).

Hemispherical, from a very thick root, often densely proliferous, transversely lined below by the remains of withered tubercles: ribs usually 8 (in young specimens often 6), very broad, gradually merging above into the distinct nascent tubercles which are crowned with somewhat delicate penicellate tufts, which become rather inconspicuous pulvilli on the ribs: flowers small, whitish to rose: stigmas 4. (Ill. Bot. Mag. t. 4296) Type unknown.

Along the Lower Rio Grande, Texas, and extending southward into San Luis Potosi and southern Mexico.