112 
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 Pass and head of the 
Limpia to E] 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; Hvans 
of 1891): SAN Luis Poros (Lschanzier 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-Dyeck in Cact. Hort. Dyek., 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 generaliza- 
tion. Dr. Engelmann speaks of this species as “a stately plant, by far the largest 
of the northern Mamillarie.” Its tubercles are bright green and in beautiful 
contrast with the showy yellow spines. 
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 em. 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, com- 
pressed, curved downwards (occasionally an additional straighter 
upper one), not much longer than the radials, the base nearly 2 mm. 
wide; all the spines horny and black-tipped: flowers 3.5 to 5 em. long, 
with very slender and constricted tube, saffron-yellow: fruit green: 
seeds large (3 to 3.2 mm. long and 2mm. in diameter), obliquely obo- 
vate and curved, smooth and brownish. (JU. Cact. Mex. Bound. t. 74, 
fig. 8, seeds)—Type, Schott specimens in Herb. Mo. Bot. Gard. 
“On grassy prairies on the south side of the Babuquibari Moun- 
tains,” 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 Kngelm. 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 horny, interwoven 
with adjacent clusters; central spine solitary (sometimes an additional 
