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 assemblage of closely related forms that seem to cluster 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 assertion. 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).