130 



THE CACTACEAE. 



24. TRICHOCEREUS (Berger) Riccobono, Boll. R. Ort. Bot. Palermo 8: 236. 1909. 



Columnar plants, more or less branched; ribs few to numerous, either low or prominent, usually 

 very spiny; flowers nocturnal, large, funnelform, the perianth either persistent or separating from 

 the fruit by abscission; perianth-segments elongated; stamens numerous, filiform, arranged in two 

 groups ; stigma-lobes numerous ; ovary and flower-tube bearing numerous scales, their axils bearing 

 long hairs; fruit without bristles or spines, dull colored. 



Type species: Cereus macrogonus Otto. 



This genus consists of 19 species, confined to South America. It is based on the sub- 

 genus of the same name by Berger, but only 2 of Berger's species were transferred to it by 

 Riccobono. 



While the flowers of this genus suggest Echinopsis, we can not agree with Berger's 

 suggestion that the genera might be united. 



The name is from the Greek and signifies thread-cereus, referring to the hairy flower- 

 areoles. 



Key to Species. 



Stems more or less branched, usually erect. 

 Limb of flower broad. 



Joints relatively slender, 5 to 9 cm. thick. 



Ribs transversely sulcate between the areoles. 



Tubercles prominent 1. T. thelegonus 



Tubercles not prominent 2. T. thelegonoides 



Ribs not transversely sulcate between the areoles. 



Central spine solitary 3. T. spachianus 



Central spines 4 4. T. lamprochlorus 



Joints stout. 



Ribs on old plants very numerous and the spines bristle-like 5. T. pasacana 



Ribs 4 to 17. 



Spines slender, 1 to 7 cm. long. 

 Ribs 4 to 9. 



Spines yellow, at least when young; ribs 4 to 8 6. T. bridgesii 



Spines brown from the first; ribs 6 to 8. 



Plant dark green; spines few at each areole or wanting 7. T. pachanoi 



Plant light green; spines several at each areole. 



Spines acicular, 2.5 cm. long or less 8. T. macrogonus 



Spines subulate, up to 7 cm. long. 



Spines swollen at base; young growth green 9. T. cuzcoensis 



Spines not swollen at base; young growth very 



glaucous 10. T. peruvianus 



Ribs r 6 or 17 11. T. chiloensis 



Spines very stout, formidable. 



Spines dark brown 12. T. coquimbanus 



Spines yellow 13. T. terscheckii 



Limb of flower narrow 14. T. fascicularis 



Stems usually simple, low, cespitose. 



Flowers red or yellow, short, more or less campanulate 15. T. huascha 



Flowers elongated, funnelform, white. 

 Tube longer than the limb. 



Ribs few, 9 to 1 1 16. T. candicans 



Ribs 12 to 18. 



Stem slender, elongated 17. T. strigosus 



Stem stout, short 1 8. T. shaferi 



Tube about the length of the limb 19. T. schickendantzii 



1. Trichocereus thelegonus (Weber). 



Cereus thelegonus Weber in Schumann, Gesamtb. Kakteen 78. 1897. 



Stems procumbent or sometimes with erect branches, elongated, 4 to 10 dm. long, dark green, 

 cylindric, 4 to 7.5 cm. in diameter; ribs 12 or 13, broad and obtuse, divided into prominent, more or 

 less distinctly 6-sided tubercles; areoles circular, felted; spines at first brown, some turning gray, 

 others black; radial spines 6 to 8, acicular, somewhat spreading, 1 to 2 cm. long; central spine solitary, 

 porrect, 2 to 4 em. long; flowers white, about 20 cm. long, funnelform; outer perianth-segments 

 greenish; axils of scales on flower- tube long-woolly; fruit about 5 cm. long, hairy, red, splitting on 

 one side; seed black. 



Type locality: Tucuman, Argentina. 

 Distribution: Northwestern Argentina. 



