40. Cactus scheerii (Muhlenpf.) Kuntze, Rev. Gen. Pl. 261 (1891). Mamillaria scheerii Muhlenpf. Allg. Gart. Zeit. xv. 97 (1847). Mamillaria scheerii valida Engelm. Syn. Cact. 265 (1856). Ovate-globose, 7.5 to 17.5 cm. high, 7.5 to 12.5 cm. in diameter, simple or sparingly proliferous at base: tubercles large (2.5 to 3.5 cm. long), from a broad base and suddenly contracted and almost cylindric (10 to 14 mm. in diameter), deeply grooved (1 to 5 orbicular glands in the groove), distant, spreading and ascending, the lower ones shorter, more conical and somewhat imbricated, with broad axils and the younger densely woolly: radial spines 6 to 16, straight or slightly curved, stout, rigid, bulbous at base, whitish or yellowish (sometimes reddish) with dark tip, the 2 to 5 lower and lateral ones stouter and compressed (18 to 30 mm. long), the 4 to 11 upper ones weaker and terete (10 to 20 mm. long); central spines 1 to 5, stout and angled, 20 to 36 mm. long,,mostly yellow (sometimes reddish), a single one very stout and porrect: flowers 5 cm. long, yellow (sometimes reddish tinged): fruit ovate or subglobose, green: seeds large (3 mm. long), flat and obovate, red. Type unknown; that of the old var. valida is the Wright material in Herb. Mo. Bot. Gard. Sandy ridges, southwestern Texas, from Eagle Pass and head of the Limpia to El Paso, and southward into Chihuahua, Coahuila, and San Luis Potosi; also southern Mexico (fide Hemsley). Fl. July. Specimens examined: Texas (Wright 416, 478, of 1851, 1852; Evans of 1891): San Luis Potosi (Eschanzier of 1891). The var. valida was described by Dr. Engelmann without having seen C. scheerii, the only knowledge of that species being obtained from the description of Prince Salm-Dyck in Cact. Hort. Dyck., which seemed to indicate a smaller form, with fewer spines than the Texan form. However, when visiting the collections of Prince Salm-Dyck, Dr. Engelmann found original specimens of C. scheerii which were exactly his var. valida. So far as collections show the Texan form seems to be more robust than the Mexican, but the material is too scanty to justify such a generalization. Dr. Engelmann speaks of this species as "a stately plant, by far the largest, of the northern Mamillariae" Its tubercles are bright green and in beautiful contrast with the showy yellow spines. 41. Cactus robustispinus (Schott) Kuntze, Rev. Gen. Pl. 261 (1891). Mamillaria robustispina Schott in Engelm. Syn. Cact. 265 (1856).