41. Cactus robustispinus (Schott) Kuntze, Rev. Gen. Pl. 261 (1891).

Mamillaria robustispina Schott in Engelm. Syn. Cact. 265 (1856).

A large stout plant, simple or cespitose: tubercles large, subterete, nearly 2.5 cm. long (and about the same distance from each other): radial spines 12 to 15, stout and rigid, 18 to 30 mm. long, the lower ones the stouter, more dusky, straight or often curved downwards, the upper straight and fascicled; the solitary central spine stout, compressed, curved downwards (occasionally an additional straighter upper one), not much longer than the radials, the base nearly 2 mm. wide; all the spines h.o.r.n.y and black-tipped; flowers 3.5 to 5 cm. long with very slender and constricted tube, saffron-yellow: fruit green seeds large (3 to 3.2 mm, long and 2 mm. in diameter), obliquely obovate and curved, smooth and brownish. (Ill. Cact. Mex. Bound.

t. 74. fig. 8, seeds) Type, Schott specimens in Herb. Mo. Bot.

Gard.

"On gra.s.sy prairies on the south side of the Babuquibari Mountains," Sonora. Fl. July.

Specimens examined: Sonora (Schott of 1853-4).

Dr. Engelmann remarks that the seeds of this species are larger than those of any other Mamillaria known to him.

42. Cactus recurvatus (Engelm.) Kuntze Rev. Gen. Pl. 259 (1891).

Mamillaria recurvispina Engelm. Syn. Cact. 265 (1856), not Vries.

Mamillaria recurvata Engelm. Trans. St. Louis Acad. ii.

202 (1863).

Globose or depressed-globose, 7.5 to 20 cm. in diameter, simple: tubercles ovate, deeply grooved, crowded, somewhat imbricate, 10 to 12 mm. long: radial spines 12 to 20, bulbous at base, compressed, rigid, recurved or flexuous, 8 to 18 mm. long, whitish or h.o.r.n.y, interwoven with adjacent cl.u.s.ters; central spine solitary (sometimes an additional upper one), stouter and longer (12 to 20 mm.), dark, mostly strongly recurved and appressed (rarely straightish): flowers about 3.5 cm. long, yellow (brownish-tinged outside): fruit unknown. Type, Schott specimens in Herb. Mo. Bot. Gard.

From Sonora to southern Mexico. Fl. June-August.

Specimens examined: Sonora (Schott of 1855).

43. Cactus salm-dyckia.n.u.s (Scheer) Kuntze. Rev. Gen. Pl. 261 (1891).

Mamillaria salm-dyckiana Scheer in Salm, Cact. Hort. Dyck. 134 (1850).

Subglobose: tubercles very broad and retuse, almost 2-parted by the tomentose groove, with axillary floccose wool: radial spines 7 or 8, very rigid, widely radiant, somewhat curved, 3 to 3.5 cm.

long, in older tubercles 3 to 6 additional slender and straight or twisted spines; the solitary central spine very stout, erect, almost 5 cm. long: flowers and fruit unknown. Type: Scheer says that this plant, brought from Chihuahua by Potts, "unfortunately perished," and the description was drawn from fragments, which in those days were not apt to be preserved.

Chihuahua.

Specimens examined: Chihuahua ("Salm of 1857 ").

The specimen referred to is in Herb. Mo. Bot. Gard., and reveals no additional characters; nor can the label be interpreted, except that it indicates that the specimen is from plants cultivated successfully in the gardens of Prince Salm-Dyck.

++ 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 cl.u.s.ters, whitish or h.o.r.n.y, 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, h.o.r.n.y or whitish (at length ashy), interwoven with adjacent cl.u.s.ters, 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 pa.s.s 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.

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 h.o.r.n.y, 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 h.o.r.n.y, 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.