148 



THE CACTACEAE. 



Type species: Echinocactus erectocentrus Coulter. 



The species which we have referred to this genus resemble in size, form, and habit the 

 species of Coryphantha much more than they do the species of Echinocactus or Ferocactus. 

 This resemblance is strengthened by definite tubercles on the ribs. Schumann referred 

 them all to Thclocactus, his very complex subgenus of Echinocactus. 



The generic name is from eylvos hedgehog, and /zao-ros breast, referring to the spiny 

 tubercles of the plant. We recognize 6 species, all from northern Mexico and the adja- 

 cent parts of the United States. They are closely interrelated. 



Key to Species. 



Areoles elongated, with more or less pectinate spines. 



One or two of the central spines different from the others. 



One central spine elongated, erect i. E. erectocentrus 



One central spine short, conic 2. E. intertextus 



Central spines several, nearly alike 3. E. dasyacanthus 



Areoles circular. 



Central spines subulate, some strongly recurved 4. E. unguispinus 



Central spines acicular. 



Globular; ribs 20 to 25 ; radial spines white 5. E. macdowellii 



Ovoid; ribs 18 to 21 ; radial spines with black tips 6. E. durangensis 



1. Echinomastus erectocentrus (Coulter). 



Echinocactus erectocentrus Coulter, Contr. U. S. Nat. Herb. 3: 376. 1896. 



Plants broadly ovoid to short-cylindric, 8 to 14 cm. high, sometimes 10 cm. broad, pale bluish 

 green; ribs 21, somewhat oblique, very low, made up of closely set tubercles; radial spines 14, straight, 

 terete, pale below, red above (in old dead plants dense and interwoven above but pectinate-appressed 

 on lower part of plant); central spines 1 or 2, elongated, erect, slightly swollen at base, more con- 

 spicuous in dead than in living plants, usually ascending, one sometimes very short and porrect; 

 flowers pinkish, 3 to 5 cm. long; stamens short, greenish yellow; style longer than the stamens, pale 

 green; stigma-lobes 8, pinkish to deep red; ovary bearing a few ovate scarious scales. (This descrip- 

 tion is from living plants and differs somewhat from Dr. Coulter's which was made from dead ones.) 



Fig. 154. Echinomastus erectocentrus. 



Fig. 155. Echinomastus unguispinus. 



Type locality: Near Benson, Arizona. 

 Distribution: Southeastern Arizona. 



Unfortunately, Dr. Coulter associated with this species a plant from Saltillo, Mexico, 

 collected by Weber; this plant has been published as Echinocactus bcguinii Weber, to which 



