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: 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. xviii. 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 cm.
broad, 2.5 to 5 cm. 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 8 mm. long, light
yellowish-brown, stout, straight, and porrect: flowers 2 to 2.5
cm. long, reddish-white: fruit incurved, 1.5 to 3 cm. long. (Ill.
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: Texas (Lindheimer of 1845, 1847, 1853; Wright
226, also collections of 1849, 1852, 1853, 1855, 1856; Bigelow of