116 
49. Cactus scolymoides sulcatus (Engeim.), 
Mamillaria suleata Engelm, Pl. Lindh. 246 (1845), not Pfeiff. (1848). 
Mamillaria strobiliformis Muhlenpf. Allg. Gart. Zeit. xvi. 19 (1818), not Scheer 
(1850). 
Mamillaria calcarata Engelm, Pl. Lindh. 195 (1850). 
Cactus calearatus 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. (Jl. 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 em. 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 clusters), ashy-white (often dusky at apex), 8 to12 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 speci- 
mens): flowers 3 to 5em. long: fruit oval, elongated, about 2 cm. long, 
green: seeds elongated-obovate, brown and smooth, about 1.8 mm, long. 
(ll. Cact. Mex, Bound. t. 10)—Type, the Wright and Bigelow speci- 
mens 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; Hvans of 1891). 
The characteristic appearance of the plant is given by the very stout and straight 
central spine standing in each cluster perpendicular to the plant body. The range 
of this species, between the Pecos and the upp: r Rio Grande, suggests another sepa- 
rated group, such as is presented by C. scolymoides sulcatus to the east, between the 
Brazos and Nueces. Very frequently specimens of C. echinus oceur 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. 
