46. Cactus radians pectenoides, var. nov. Differs in its cespitose habit, fewer (16 or 17) and stouter spines (8 to 9 mm. long), and its larger and longer (10 mm.) less deeply grooved tubercles. Type in Herb. Coulter. San Luis Potosi. Specimens examined: San Luis Potosi (Eschanzier of 1891). 47. Cactus corniferus (DC.) Kuntze, Rev. Gen Pl. 260 (1891). Mamillaria cornifera DC. Rev. Cact. 111 (1829). Mamillaria impexicoma Lem. Hort. Monov. Cult. 5 (1839). Mamillaria cornifera impexicoma Salm. Cact. Hort. Dyck. 20 (1850). Globose, 7.5 cm. in diameter, simple: tubercles oblong-ovate, 2 cm long, crowded, the younger axils woolly: radial spines 15 to 26, rigid and horny, curved or sometimes straight, reflexed, bulbous at base, yellowish (whiter with age) and with dark tips, very sharp, 10 to 12 mm, long; the central one much stouter, darker, slightly deflexed, 12 to 16 mm long, sometimes wanting: flower unknown: fruit obovate, red, 2 cm long: seeds reddish, angular, smooth, 2 mm. long. Type unknown. From San Luis Potosi to southern Mexico. Specimens examined: San Luis Potosi (Parry of 1879; Eschanzier of 1891): also specimens cultivated in Mo. Bot. Gard. in 1892; growing in same garden in 1893. Mamillaria impexicoma Lem., afterwards reduced to a variety, was based upon fewer radial spines and no central. As the central is occasionally wanting in connection with the most numerous radials, and present with the fewest, such a form would have to be separated solely on the absence of the central spine, and even in the original description of impexicoma the central spine is only said to be "sometimes wanting." It has been impossible for me to separate the forms. It should be said that the fruit and seed characters given above were taken front a specimen whose few radials and no centrals would undoubtedly refer it to impexicoma. As yet we are ignorant of the flower of C. corniferus. For discussion of relationships see under C. scolymoides. ++ Central spines 1 to 4. 48. Cactus scolymoides (Scheidw.) Kuntze. Rev. Gen. Pl. 261 (1891). Mamillaria scolymoides Scheidw Allg. Gart. Zeit. ix. 44 (1841). Globose or ovate, 5 to 7.5 cm. high. subsimple: tubercles conical, 10 to 16 mm. long, the upper elongated, incurved and imbricate: radial spines 14 to 20, straight or often recurved, white or horny, 10 to 20 mm. long (the upper the longer); central spines 1 to 4, longer (18 to 32 mm.), more dusky, curved, the upper ones turned upwards and intermixed with the radials, the lower one stouter, longer, and curved downwards: flowers 5 cm. long: fruit unknown. Type unknown. From the Pecos River, western Texas, westward into southern New Mexico, and southward into Chihuahua and San Luis Potosi. Specimens examined: Texas (Hays of 1858): New Mexico (Bigelow of 1853): Chihuahua (Wislizenus of 1846): also specimens cultivated in St. Louis in 1858.