Specimens collected by Mrs. Anna B Nickels across the Rio Grande from Laredo, Texas, and showing neither flower nor fruit, seem to intergrade between C. scolymoides and C. scolymoides sulcatus.

The habit is that of the former, the tubercles are those of the latter, while the spines are somewhat different from either. The number of central spines in these specimens is very hard to determine, as on the adult tubercle they all a.s.sume a radial position. The usual adult arrangement is an apparent absence of central spines; 10 to 12 rigid, spreading and more or less recurved radials (increasing in length from the lowest), which are mostly white or the upper more or less dusky; and above, just behind the radial row, 2 or 3 stout recurved-ascending spines, which are white with tips more or less reddish-black, one of the spines usually much stouter and longer than the others. This form may represent a distinct species, but it seems very unsafe to add species to the C. scolymoides group without the fullest information.

Prince Salm-Dyck refers C. scolymoides to "M. daimonoceras Lem.

Cact. gen. nov., p. 5," but no mention of such a name can be found in the work referred to. Labouret refers C. corniferus to the same name and reference. If "M. daimonoceras" was anything more than a garden or herbarium name used by Lemaire I have been unable to find it, and Dr. Engelmann's notes indicate that his search met with the same result. It is possible that the name was applied loosely to this a.s.semblage of closely related forms that seem to cl.u.s.ter about C. corniferus.

A most perplexing question of relationship is presented by the forms that have been called pectinatus, scolymoides, sulcatus (calcaratus), Echinus, and the Mexican forms radians, impexicomus, corniferus. It may be that they are all merely varieties of one strong polymorphic type, but our knowledge of corniferus is so incomplete, and material of other forms is so scanty, that I can not venture to make such an a.s.sertion.

However, it seems probable that radians, pectinatus, scolymoides, sulcatus and Echinus all have green fruit, while in impexicomus and corniferus it is red. It has also seemed proper to merge radians and pectinatus, also impexicomus and corniferus, and to refer sulcatus to scolymoides as a variety. These seven forms are thus reduced at least to four species.

49. Cactus scolymoides sulcatus (Engelm.).

Mamillaria sulcata Engelm. Pl. Lindh. 246 (1845), not Pfeiff.

(1848).

Mamillaria strobiliformis Muhlenpf. Allg. Gart. Zeit. xvi. 19 (1848), not Scheer (1850).

Mamillaria calcarata Engelm. Pl. Lindh. 195 (1850).

Cactus calcaratus Kuntze, Rev. Gen. Pl. 259 (1891).

Differs in its smaller size; proliferous and much more cespitose habit, the dilated base of the more spreading tubercles, fewer (8 to 12) radial spines, usually a single central spine (wanting in young plants) and somewhat larger flowers. (Ill. Cact. Mex.

Bound. t. 74. fig. 1, seeds) Type, Lindheimer of 1844 in Herb.

Mo. Bot. Gard.

Texas, from the Brazos to the Nueces.

Specimens examined: Texas (Lindheimer of 1844; Fendler 34; Wright of 1850, 1854, 1857): also specimens cultivated in St. Louis in 1845, 1848, 1853, 1859.

This seems to represent the northeastern extension of the species, and doubtless it will be found merging into it south and west of the Nueces. Curiously enough one of the prominent distinctions originally given was the single central spine, while in the type specimen there occur tubercles with more than one central.

50. Cactus echinus (Engelm.) Kuntze, Rev. Gen. Pl. 260 (1891).

Mamillaria echinus Engelm. Syn. Cact. 267 (1856).

Globose or subconical, 3.5 to 6.5 cm. in diameter, simple: tubercles terete, conical, grooved above, 10 to 12 mm. long: radial spines 16 to 30, pectinate, straight or little curved, rigid and appressed (interwoven with neighboring cl.u.s.ters), ashy-white (often dusky at apex), 8 to 12 mm. long, the uppermost longer (12 to 20 mm.); central spines 3 or 4, the upper ones turned upward and intermixed with the radials, the lower one very stout, 15 mm. long, subulate from a very thick bulbous base, straight (rarely slightly curved) and porrect (deciduous in old specimens): flowers 3 to 5 cm. long: fruit oval, elongated, about 2 cm. long, green: seeds elongated-obovate. brown and smooth, about 1.8 mm. long. (Ill. Cact. Mex. Bound. t. 10) Type, the Wright and Bigelow specimens in Herb. Mo. Bot. Gard.

On limestone hills, from the Pecos River, southwestern Texas, and southern New Mexico, westward to the Rio Grande (from Presidio del Norte northward). Fl. June.

Specimens examined: Texas (Wright of 1849, 1851, 1852; Bigelow of 1852; Engelmann, with no number or date; Evans of 1891).

The characteristic appearance of the plant is given by the very stout and straight central spine standing in each cl.u.s.ter perpendicular to the plant body. The range of this species, between the Pecos and the upper Rio Grande, suggests another separated group, such as is presented by C. scolymoides sulcatus to the east, between the Brazos and Nueces. Very frequently specimens of C. echinus occur in which some of the tubercles do not develop central spines, and then the spine characters resemble those of C. radians. In C. radians, also, an occasional porrect central spine is found. These intergrading forms I have only seen in Mexican material. For discussion of relationships see under C. scolymoides.

** Flowers red.

+ Central spine solitary or sometimes wanting.

51. Cactus dasyacanthus (Engelm.) Kuntze, Rev. Gen. Pl. 259 (1891).

Mamillaria dasyacantha Engelm. Syn. Cact. 268 (1856).

Subglobose, 3.5 to 6.5 cm. high, simple: tubercles slender and terete, spreading, lightly grooved even to the base, 8 to 10 mm, long: radial spines 30 to 50, mostly in two series, straight and loosely spreading, the exterior ones (25 to 35) capillary and white, 6 to 18 mm. long, the interior ones (7 to 13) stiffer (setaceous), longer and darker and black-tipped; the central spine straight and porrect, 12 to 20 mm. long, often wanting: flowers small, red: fruit ovate, small (8 to 10 mm. long?): seeds globose-angled, almost black, pitted, 0.8 to 1.2 mm. long (Ill.

Cact. Mex. Bound. t. 12. figs. 17-22) Type, Wright 110 in Herb.

Mo. Bot Gard.

From Eagle Pa.s.s, Texas, westward to El Paso and southern New Mexico, and southward into Chihuahua.

Specimens examined: Texas (Wright 110 of 1852): New Mexico (Vasey of 1881; Mearns of 1892, in Big Hatchet Mountains) Chihuahua (Pringle 251 of 1885, in part).

Pringle 251 as distributed to Nat. Herb. is C. tuberculosus.

52. Cactus maculatus, sp. nov.

Obovate-cylindrical, 6 by 8 cm., somewhat cespitose: tubercles ovate, terete, 10 mm. long, grooved to the base, with naked axils: radial spines 10 or 11, straight and spreading, rigid, blackish (becoming ashy with age), black-tipped, 12 mm. long; central spine large, more or less spotted, erect, 25 to 35 mm.

long: flower 13 mm. long, pinkish: fruit unknown. Type in Herb.

Coulter.

San Luis Potosi.

Specimens examined: San Luis Potosi (Eschanzier of 1891).

Somewhat resembles C. tuberculosus in general appearance, but very different in spine characters.

53. Cactus brunneus, sp. nov.

Obovate-cylindrical, 3 by 6 cm., simple: tubercles ovate, grooved to the base, 5 to 6 mm. long, with woolly axils: radial spines 11 to 15, spreading, rather rigid and brownish (lighter with age), 8 to 10 mm. long; central spine much larger, 20 mm, long, hooked: flower and fruit unknown. Type in Herb. Coulter.

San Luis Potosi.

Specimens examined: San Luis Potosi (Eschanzier of 1891).

++ Central spines 3 to 12.

54. Cactus conoideus (DC.) Kuntze, Rev. Gen. Pl. 260 (1891).

Mamillaria conoidea DC. Rev. Cact. 112 (1829).

Mamillaria strobiliformis Engelm. Wisliz. Rep. 113 (1848), not Scheer (1850).

Ovate-conical, 3.5 to 10 cm. high, 4 to 7 cm. in diameter below, with densely woolly vertex, simple: tubercles conical, about 12 mm, long, closely appressed-imbricate ("giving the plant the appearance of a pineapple or cone"): radial spines 10 to 16, ashy to white, straight and stout, 6 to 10 mm. long, the upper longer (10 to 15 mm.); central spines 3 to 5, stouter, brownish-black, 10 to 16 mm. long, the two or three smaller ones erect-spreading, the single lower one more rigid, porrect or deflexed, 15 to 20 mm. long: flowers 2 to 3 cm long and wide, deep purple: fruit unknown. (Ill. DC. Mem. Cact. t. 2) Type unknown.

On rocks, Coahuila and Nuevo Leon to San Luis Potosi and southern Mexico.

Specimens examined: Coahuila (Palmer 378 of 1882; Pringle 3117 of 1890): Nuevo Leon (Wislizenus of 1847): San Luis Potosi (Poselger of 1851; Eschanzier of 1891).

55. Cactus potsii (Scheer) Kuntze, Rev. Gen. Pl. 261 (1891).

Mamillaria potsii Scheer in Salm Cact. Hort. Dyck. 104 (1850).

Cylindrical, 30 to 35 cm. high, 2.5 to 3 cm. in diameter, somewhat branching: tubercles ovate, obtuse, very lightly sulcate, with somewhat woolly axils: radial spines very numerous (entirely covering the whole plant), slender and white; central spines 6 to 12, stouter from a broad base: flowers large, green, or reddish: fruit red. Type unknown.

From the Rio Grande region, near Laredo, Texas, to Chihuahua.

Specimens examined: Texas (Poselger of 1851): Chihuahua (specimens from Coll. Salm-Dyck.).

56. Cactus tuberculosus (Engelm.) Kuntze, Rev. Gen. Pl. 261 (1891).