lO 



THE CACTACEAE. 



8. Thelocactus fossulatus (Scheidweiler). 



Echinocactus fossulatus Scheidweiler, AUg. Gartenz. 9: 49. 1841. 



Echinocacliis hexaedrophorus subcostatus Salm-Dyck, Cact. Hort. Dyck. 1849. 34. 1850. 



Echinocactus hexaedrophorus fossulatus Salm-Dyck in Labouret, Monogr. Cact. 251. 1853. 



Globose to much depressed, 10 to 15 cm. in diameter; ribs usually 13, slightly glaucous, bronzed; 

 tubercles large, somewhat flabby, more or less compressed, dorsally somewhat angled; flowering 

 areoles narrow, sometimes extending forward to next tubercle; radial spines 4 or 5, unequal, i to 

 3.5 cm. long, brown; central spine solitary, 3 to 4.5 cm. long, subulate, annulate; flowers nearly 

 white or slightly tinged with pink; scales on flower-tube ovate, their scarious margins slightly 

 ciliate. 



Type locality: Near San Luis Potosi, Mexico. 

 Distribution: San Luis Potosi, Mexico. 



Fig. 8. — Thelocactus nidulans. 



Fig. 9. — Thelocactus fossulatus. 



Somewhat similar to the foregoing species is C. A. Purpus's No. 15 from Minas de San 

 Rafael, Mexico. This plant has more rounded tubercles, only 4 spines, these all radial and 

 2 cm. long or less, somewhat flattened. 



Thelocactus fossulatus is certainly distinct from Thelocactus hexaedrophorus, differing 

 in the arrangement of the tubercles and in the color of the flowers. The former is from 

 an altitude of 7,000 feet, while the other is from near sea-level. 



Echinocactus drageanus (Moerder, Rev. Hort. 67: 186. 1895) and ii. droegeanus Hild- 

 mann (Schumann, Gesamtb. Kakteen 438. 1898) probably belong here, although the latter 

 is referred by Schumann to Echinocactus hexaedrophorus. This may be the plant, judging 

 from the name and authorities mentioned, which Schelle (Handb. Kakteenk. 257. 1907) 

 refers to as Mammillaria rhodantha droegeana Schumann (M. droegeana Hildmann) . Schelle 

 questions whether it may not be a distinct species, presumably a Mammillaria. 



Illustrations: Scientific Amer. 124: 492, as Echinocactus; Curtis's Bot. Mag. 73: pi. 

 4311 ; Ann. Rep. Smiths. Inst. 1908: pi. 13, f. 3, as Echinocactus hexaedrophorus; Pfeiffer, 

 Abbild. Beschr. Cact. 2: pi. 13, as Echinocactus fossulatus; Monatsschr. Kakteenk. 27: 41, 

 as Echinocactus hexaedrophorus droegeanus. 



Figure 9 is from a photograph of a plant collected by Dr. Edward Palmer at San Luis 

 Potosi, Mexico, in 1905. 



