THELOCACTUS. 9 



Densely cespitose, short-cylindric, 10 to 15 cm. long; ribs 8 to 13, sometimes spiraled, obtuse, 

 tubercled; radial spines 7 to 20, at first light yellow, in age gray, spreading or recurved, unequal, 

 the longer ones 4 cm. long, more or less annulate; central spine solitary, at first blackish, but in age 

 gray, up to 5 cm. long; flowers yellow, 5 cm. long; inner perianth-segments numerous, lanceolate, 

 acute; ovary and flower- tube bearing broad imbricated scales. 



Type locality: Near Zimapan, Mexico. 



DistHhution : Zimapan and Ixmiquilpan, Mexico. 



We are inclined to refer here Echinocactus ehrenhergii Pfeiffer (Allg. Gartenz. 6: 275. 

 1838), which, according to Schumann, also came from Ixmiquilpan, Mexico. In his mono- 

 graph Schumann describes the flowers as yellow like those of E. leucacanthiis, but in his 

 English Keys he says that the flowers are rose-red. Dr. Rose, who collected in this region 

 in 1905, found only one species of this relationship. 



Fig. 6. — Thelocactus buekii. 



; leucacanthus. 



Echinocactus ttiberosus Salm-Dyck (Forster, Handb. Cact. 287. 1846) is known only as 

 a synonym. 



Echinocactus tuherosus subporrectus (Forster, Handb. Cact. 523. 1846) belongs here. 



Illustrations: Pfeiffer and Otto, Abbild. Beschr. Cact. i: pi. 14; Abh. Bayer. Akad. 

 Wiss. Mtinchen 2: pi. 2, f. 10; pi. 3, f. 4, as Echinocactus leucacanthus. 



Figure 7 is from a photograph of the plant collected by Dr. Rose at Ixmiquilpan in 

 1905- 



7. Thelocactus nidulans (Quehl). 



Echinocactus nidulans Quehl, Monatsschr. Kakteenk. 21: 119. 191 1. 



Simple, depressed-globose, 10 cm. high, sometimes 20 cm. in diameter, gray, usually glaucous; 

 ribs 20 to 25, rather indistinct, divided into tubercles; spines about 15, all similar, 2 to 6 cm. long; 

 flowers 4 cm. long, yellowish white. 



Type locality: Mexico. 



Distribution: Mexico, but known only from cultivated plants. 



Illustrations: Monatsschr. Kakteenk. 22: 51; AHanza Cientifica Universal 3: 114, as 

 Echinocactus nidulans. 



Figure 8 is from a photograph given to Dr. Rose by Frantz de Laet in 1912. 



