++ Flower and fruit remaining central in the very woolly vertex of the plant. ++ Central spine solitary or wanting. 44. Cactus compactus (Engelm.) Kuntze Rev. Gen. Pl. 260 (1891). Mamillaria compacta Engelm. Wisliz. Rep. 21 (1848). Depressed-globose, 5 to 10 cm. in diameter, simple: tubercles short-conical, crowded, 8 mm. long: radial spines 13 to 16, rigid, recurved and appressed, interwoven with adjacent clusters, whitish or horny, 10 to 20 mm. long; the erect central spine often wanting: flowers 3 to 3.5 cm. long and broad, yellow (brownish without): fruit oval, green: seeds 1.4 mm. long, smooth and yellow. (Ill. Cact. Mex. Bound. t. 74. fig. 2, seeds) Type, Wislizenus of 1846 in Herb. Mo. Bot. Gard. Mountains of Chihuahua. Fl. June-July. Specimens examined: Chihuahua (Wislizenus of 1846): also specimens cultivated in St. Louis in 1848, 1850, 1854. 45. Cactus radians. (DC.) Kuntze, Rev. Gen. Pl. 261 (1891). Mamillaria radians DC. Rev. Cact. 111 (1829). Mamillaria pectinata Engelm Syn. Cact. 266 (1856). Globose, 3.5 to 7.5 cm. in diameter, simple: tubercles conical, from a 4-angled base, lower ones short (4 to 6 mm.), upper flower-bearing ones longer (10 to 12 mm.), terete and grooved: radial spines 16 to 24, somewhat recurved from a bulbous compressed base, stiff and pectinate, horny or whitish (at length ashy), interwoven with adjacent clusters, those on lower tubercles about equal (6 to 10 mm.), on flower-bearing tubercles elongated, mixed with a few stouter ones and fasciculated (lower ones 10 to 12 mm. long, upper ones 12 to 18 mm. long and forming an apical tuft); centrals none: flowers over 5 cm. long and about 6 to 7.5 cm. in diameter when expanded, bright sulphur-yellow: fruit ovate and green, about 12 mm. long: seeds compressed, brownish smooth and shining, 1.8 mm. long. (Ill. Cact. Mex. Bound. t. 11) Type unknown; that of M. pectinata Engelm. is the Wright material in Herb. Mo. Bot. Gard. Extending from the hills along the Lower Pecos to El Paso, southwestern Texas, southward through Coahuila and San Luis Potosi to southern Mexico. Specimens examined: Texas (Wright 226 of 1849, also of 1852; Evans of 1891): Coahuila (Palmer of 1880; Mrs. Nickels): San Luis Potosi (Parry & Palmer 265; Eschanzier of 1891): also specimens cultivated in St. Louis in 1853; in Mo. Bot. Gard. in 1892; and in Harv. Bot Gard. Even in the absence of the type I have ventured to refer Mamillaria pectinata Engelm. to this species. Dr. Engelmann had concluded that the two were "not sufficiently distinct," and the examination of Mexican forms which pass as C. radians abundantly confirms this conclusion. Besides, every character in the original description of C. radians applies exactly to these Mexican plants and to our Texan specimens as well. Aside from the fact that the Mexican specimens are apt to be more robust, I can discover no difference whatever. For discussion of relationships see under C. scolymoides.