CACTACE^ OF MEXICO SAFFORD. 



559 



Thelocactus, with the surface covered with tubercles more or less 

 confluent, as in Echinocactus lopliothele (pi. 3, fig. 1) and E. rin- 

 conadensis, or 5 or 6 sided, as in E. hexaedroj^lwriis (pi. 13, fig. 5). 



3. Leuchtenhergia. — This genus, which is represented by a single 

 species, L. prineipis^ stands quite alone among the Cactacese. It has 

 a woody stem bearing long prismatic tubercles very much like those 

 of certain INIamillarias, but the flower has a scaly tube more like that 

 found in the genus Echinocactus. The tubercles are arranged spi- 

 rally and are at length deciduous, their bases leaving the stem scarred 

 very much like that of a Zamia after its leaves have fallen. The 

 areoles, situated at the tips of the tubercles, are cottony or woolly 

 when young and bear a tuft of flexible papery or strawlike spines, 

 The large axillary brownish-yellow fragrant flowers appear from 

 among the young tubercles near the crest of the plant. The stamens 

 are numerous, the outer ones 

 growing together and con- 

 nate with the tube of the 

 perianth, which they close, 

 their upper parts free and 

 closely fascicled around the 

 style, which exceeds them 

 slightly in length, bearing 

 a 10-14-rayed bright yellow 

 stigma. This species is used 

 by the Mexicans as a rem- 

 edy for certain diseases of 

 animals, and at one time 

 was gathered in such quan- 

 tities as to threaten its ex- 

 tinction. It has been col- 

 lected in the vicinity of 

 Pachuca, Hidalgo ; south- 

 east of San Luis Potosi; and in the vicinity of Patagallina, southeast 

 of Parras, Coahuila. 



4. Cactus {Melocactus). — The plants of this genus, often called 

 turk's-cap or turk's-head, are fleshy and globose, or oval, usually 

 ribbed like a melon and bearing tufts of rigid spines very much like 

 those of an Echinocactus. It differs, however, from that genus in 

 having a distinct cylindrical cap, or cephalium, composed of woolly 

 felt and fine bristles, from which issue the numerous small incon- 

 spicuous flowers and at length the fruit. The latter is red, smooth, 

 and club shaped, very closely resembling the chilitos of certain Mamil- 

 larias, and, like them, pleasantly acidulous and edible. The genus is 

 principally West Indian and tropical American. A photograph of 

 Cactus maxonii {Melocactus maxonii Giirke), showing a single fruit 

 and several flowers, is reproduced on plate 2, figure 2. 



Fig. 23. — Leuchtenhergia principis. 



