4 
THE CACTACEAE- 
In habit it simulates the South American genus, Echinopsis, while in flowers and fruits 
it comes near Erdisia, Bergerocactus, and Wilcoxia. While all the species are low in habit 
there is great variation in the manner and form of growth. Some are solitary; others grow 
in flat masses, and others in large rounded mounds. The flowers, while always having 
a spiny ovary and flower-tube and green stigma-lobes, have considerable variation in 
the shape and color of perianth-segments and in duration. The flower-buds as well as 
the young shoots are deep-seated in their origin and do not appear just at the areoles as 
in most cacti and hence must break through the epidermis when they develop. A some¬ 
what similar result is produced in the flowering of some of the species of Rhipsalis. Echino- 
cereus has been selected as the state flower of New Mexico. 
Most plants of Echinocereus do not flower frequently in greenhouse cultivation. 
The species are not readily grouped into series; our classification of them is largely 
artificial, taking flower-color as a more important character than it probably is in nature. 
Key to Species. 
A. Flowers large, usually conspicuous, rarely only 2 to 3 cm. long. 
B. Stems covered with long weak bristles or hairs, resembling a small plant of Ceph- 
alocereus senilis . 
BB. Stems variously covered with spines or rarely spineless, never like the above. 
C. Flowers scarlet to salmon-colored, opening once, but lasting for several days. 
Stems usually weak, often trailing, or at least becoming prostrate; ribs nearly con¬ 
tinuous. 
Flowers rosy red. 
Flowers orange-red to salmon-colored. 
Flowers 8 to n cm. long; wool from areoles on flower-tube long. 
Flowers 8 to 10 cm. long; radial spines 9 or fewer. 
Flowers n cm. long; radial spines 10 to 12. 
Flowers 6 cm. long or less; wool from areoles on flowers shorter than subtending 
scale. 
Stems usually erect and stout; ribs more or less tubercled. 
Plants forming large mounds, Sbmetimes with 500 to 800 joints; spines white, long 
and flexuous. 
Plants in much smaller clusters; spines brownish or grayish, not long and flexuous. 
Plant body with 12 to 14 ribs. 
Plant body with 5 to n ribs (in one species 12). 
Ribs 5 to 8. 
Ribs 9 to 12. 
Axils of flower-scales filled with long cobwebby hairs. 
Flowers 5 to 6 cm. long; spines yellowish at first. 
Flowers 3 cm. long; spines reddish at first. 
Axils of flower-scales bearing short hairs. 
Stems elongated and thinner than in E. octacanthus . 
Stems short and thicker than in E. acifer. 
Stems pure green when old; central spine 1. 
Stems bluish green; central spines several. 
Central spines 6; petals acutish. 
Central spines mostly 4, sometimes 3 or 5. 
Central spines more or less angled, somewhat curved. 
Central spines terete, straight. 
Central spines white or straw-colored. 
Central spines gray to pinkish. 
CC. Flowers broad, rotate to campanulate, opening in sunlight, closing at night, usually 
purple, sometimes yellow or greenish yellow, rarely pink or 
nearly white, unknown in E. standleyi. 
D. Flowers yellow or greenish white. 
Ribs not strongly tubercled. 
Plants densely cespitose. 
Plants usually solitary. 
Ribs very stout. 
Ribs 5 to 8; spines on flower-tube and ovary short. 
Ribs 8 or 9; spines on flower-tube and ovary acicular. 
Ribs low, usually hidden by the spines. 
Flowers small, 2.5 cm. long or less. 
Areoles circular. 
Areoles elliptic. 
Flowers large, 5 to 10 cm. long. 
Flowers greenish white. 
Flowers yellow-red. 
1. E. delaetii 
2. E. scheeri 
3. E. salm-dyckianus 
4. E. huitcholensis 
5. E. pensilis 
6. E. mojavensis 
7. E. lecanus 
8 . E. triglochidiatus 
9. E. polyacanthus 
10. E. pacificus 
11. E. acifer 
12. E. octacanthus 
13. E. neo-mexicanus 
14. E. conoideus 
15. E. coccineus 
16. E. rosei 
17. E. maritimus 
18. E. subinermis 
19. E. luteus 
20. E. chloranthus 
21. E. viridiflorus 
22. E. grandis 
