longimamma centrals often more than one and somewhat longer).

34. Cactus gabbli, sp. nov.

Mamillaria gabbii Engelm Mss.

Globose, 5 to 10 cm. in diameter, simple: tubercles cylindrical, slender, 12 to 14 mm. long, with woolly axils: radial spines about 13, 5 to 8 mm. long, lower ones longer and stouter, especially the lateral ones pectinate; the central shorter, straight, and robust: flowers small, yellowish-red: fruit unknown. Type in Herb. Mo. Bot. Gard.

Among rocks, from San Ignacio to Mission San Fernando, Lower California, and "perhaps farther north in the interior."

Specimens examined: Lower California (W. M. Gabb 19 of 1867).

35. Cactus sphaericus (Dietr.) Kuntze, Rev. Gen Pl. 261 (1891).

Mamillaria sphaerica Dietr. Allg. Gart. Zeit xxi. 94 (1853).

Obovate or clavate, 5 cm. or more high, proliferous and at length densely cespitose: tubercles elongated-ovate, acutish, 12 to 10 mm. long with axillary wool: radial spines 12 to 14, setaceous, 7 to 9 mm. long, bulbous at base, straight or curved, white; central spine straight, subulate, somewhat shorter, but scarcely stouter: flowers yellow, 3.5 to 5 cm. long: fruit unknown. Type unknown.

Sandy ridges in the valley of the Rio Grande (both sides of the river), from the mouth to Eagle Pa.s.s. Fl. from March throughout the season.

Specimens examined: Texas (Schott of 1852): also specimens cultivated in St. Louis in 1845 and 1861.

Dietrich's description was taken from plants collected by Poselger at Corpus Christi. The Schott specimens are from Eagle Pa.s.s. Dr. Engelmann calls attention to the fact that this species approaches Coryphantha in its exserted ovary and large flower, but the flowers are clearly from the growth of the preceding season. The species is said to be too near the Mexican C. longimamma of central and southern Mexico, but in the absence of type specimens of either the question can not be settled. The usual characterization of C. longimamma is as follows, which seems to make it distinct enough:

36. Cactus longimamma (DC.) Kuntze, Rev. Gen. Pl. 260 (1891).

Mamillaria longimamma DC. Rev. Cact. 113 (1829).

Ovate or at length cylindrical, simple or cespitose: tubercles oblong-ovate, large at base, 4 to 5 cm. long: radial spines 7 or 8, radiant and equal, 8 to 10 mm. long or more, more or less p.u.b.escent; central spines 1 to 3, somewhat longer and spreading: flower 4 cm. long, becoming 6 cm. broad when fully expanded, yellow. (Ill. DC. Mem. Cact. t. 5.)

II. CORYPHANTHA. Flowers from the base of a groove on young or nascent tubercles (hence appearing terminal), mostly large: spines never hooked (except in the doubtful C. brunneus).

* Flowers yellow.

+ The originally central flowers pushed aside by the continuous development of new tubercles: usually a single prominent central spine.

37. Cactus missouriensis (Sweet) Kuntze, Rev. Gen. Pl. 259 (1891).

Cactus mamillaris Nutt. Gen. i. 295 (1818), not Linn. (1753).

Mamillaria missouriensis Sweet, Hort. Brit. 171 (1827).

Mamillaria simplex Torr. & Gray, Fl. N. Am. i. 553 (1840).

Mamillaria nuttallii Engelm. Pl. Fendl. 49 (1849).

Mamillaria notesteinii Britton, Bull. Torr. Bot. Club, xviii, 367 (1891).

Globose, 3.5 cm. in diameter, simple or nearly so: tubercles ovate-cylindrical, 12 to 14 mm. long, slightly grooved: radial spines 13 to 17, straight, whitish, setaceous, somewhat unequal, 8 to 10 mm. long; central spine more robust, straight and porrect, p.u.b.erulent, 10 to 12 mm. long, often wanting: flowers about 2.5 cm. long, yellow or reddish: stigmas 2 to 5: fruit globose, scarlet, 6 to 8 mm. in diameter: seeds globose, black and pitted, 0.8 to 1.1 mm. in diameter. (Ill. Cact. Mex. Bound.

t. 74., f. 6, seeds.) Type unknown.

High prairies of the Upper Missouri, from Montana to South Dakota and southward through western Nebraska to western Kansas and the eastern slopes of the mountains of Colorado. Fl. May.

Specimens examined: Montana (Notestein of 1893): National Park (Tweedy 423): South Dakota, (collector unknown, in 1847, 1848, 1853): Nebraska (Hayden of 1855).

38. Cactus missouriensis similis (Engelm.).

Mamillaria similis Engelm. Pl. Lindh. 246 (1845).

Mamillaria nuttallii caespitosa Engelm. Syn. Cact. 265 (1856).

Mamillaria missouriensis caespitosa Watson, Bibl. Index, 403 (1878).

Cespitose, with 12 to 15 p.u.b.erulent radial spines, the central very often wanting, larger flowers (2.5 to 5 cm. long), fruit and seeds (1.6 to 2.2 mm. in diameter), and 5 stigmas. (Ill. Cact.

Mex. Bound. t. 74. f 7, seeds) Type, Lindheimer, of 1845 (?) in Herb. Mo. Bot. Gard.

From the Kansas River, Kansas, and eastern Colorado, southward through Oklahoma to the San Antonio River, Texas.

Specimens examined: Colorado (Greene of 1870): Kansas (Carleton 551 of 1891, from Kingman County, distributed as Mamillaria dasyacantha): Oklahoma (Carleton 120 of 1891): Texas (Lindheimer of 1845, 1850; Wright of 1850; Reverchon 725): also specimens cultivated in Goebel's Garden in 1846; and in St. Louis in 1846, 1847, 1851.

The cespitose ma.s.ses are often a foot broad.

39. Cactus missouriensis robustior (Engelm.).

Mamillaria similis robustior Engelm. Pl. Lindh. 200 (1850).

Mamillaria nuttallii robustior Engelm. and Bigel. Pacif. R.

Rep. iv. 28 (1856).

Mamillaria missouriensis robustior Watson, Bibl. Index, 440 (1878).

Almost simple, with longer aid looser tubercles, 10 to 12 stouter radial spines (6 to 16 mm. long), a single stout central, larger flowers, and 7 or 8 stigmas. Type, Lindheimer of 1845 in Herb.

Mo. Bot. Gard.

From southeastern Colorado and the Canadian River (Oklahoma and Indian Territory), to the Colorado River of Texas.

Specimens examined: Texas (Lindheimer of 1845, 1846; Bigelow of 1853): also specimens cultivated in St. Louis in 1847.

In Bigelow's specimens the central spine is mostly lacking.

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 Pa.s.s 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.