97 
San Luis Potosi. 
Specimens examined: SAN Lurs Porost (Fschanzier of 1891). 
Very easily distinguished by its dense, erect spines, which so completely cover 
the plant as to give it the appearance of a large chestnut bur, Another much 
smaller form, which seems to be a variety, has stouter and longer ashy-white spines, 
the centrals darker-tipped, and the lower centrals slightly curved. 
+ + One short central spine (rarely two or none): ovaries immersed: seeds small, yellow 
and rugulose: juice milky: simple. 
5. Cactus heyderi (Muhlenpf.) Kuntze, Rev, Gen. Pl. 260 (1891). 
Mamillaria heyderi Muhlenpf. Allg. Gart. Zeit. xvi. 20 (1848). 
Mamillaria declivis Dietr. Allg. Gart. Zeit, xvili. 235 (1850). 
Mamillaria applanata Engelm. Pl. Lindh. 198 (1850). 
Mamillaria texensis Labouret, Monogr. Cact. 89 (1858). 
Depressed-globose, usually with depressed vertex, 8 to 12 em. broad, 
2.5 to 5 em. high: tubercles elongated: radial spines 10 to 22, whitish, 
5 to 12 mm. long, the lower usually the longer, stouter, and often 
darker; central spine 4 to 5 mm. long, light yellowish-brown, stout, 
straight, and porrect: flowers 2 to 2.5 em. long, reddish-white: fruit 
incurved, 1.5 to 3 cm. long. (IU. Cact. Mex, Bound. t. 9. figs, 4-14)— 
Type unknown. 
From the Guadalupe River, Texas, to the mouth of the Rio Grande, 
and westward to Arizona and Sonora, Fl. April, May. 
Specimens examined: TPXAS (Lindheimer of 1845, 1847, 1853; Wright 
226, also collections of 1849, 1852, 1853, 1855, 1856; Bigelow of 1853; 
Trelease of 1892; Nealley of 1892): New MuExico (Wright 311; Bige- 
low of 1853; Evans of 1891): Arizona (Pringle of 1881): also growing 
in Mo. Bot. Gard. 1893; and in the World’s Fair collection of Afrs. 
Nickels. . 
The radial spines are somewhat variable in relative length, often becoming almost 
equal, while sometimes the upper radials are very much reduced. ‘The figure referred 
to in Cact. Mex. Bound. is not satisfactory as to the general habit of the plant, which 
is flat-topped rather than hemispherical. ; 
6. Cactus heyderi hemisphzricus (Engelm.). 
Mamillaria hemispherica Engelm. Pl. Lindh, 198 (1850). 
Differs in being hemisplierical instead of flat-topped, in its fewer 
(9 to 12) and shorter (4 to 8 mm.) radial spines, and much smaller less 
rough and lighter-colored seeds. (I/l.Cact. Mex. Bound. t.9. figs. 19-17) — 
Type, the “ Goebel’s Garden” plants in Herb, Mo. Bot. Gard. 
Throughout southern Texas and southern New Mexico, and south- 
ward; not extending so far north or west as the species, and apparently 
not so abundant within the United States. Fl. May. 
Specimens examined: TEXAS (Schott 322, 614): NEw MExico (vans 
of 1891): also specimens cultivated in the Goebel Garden, St. Louis, in 
1847, brought from “below Matamoras on the Rio Grande” by the St. 
Louis Volunteers, in 1846, 
On account of its convex top the variety becomes somewhat higher than the 
species (5 to 7.5 cm.), and the flowers are sometimes slightly longer (2 to 3 cm.). 
