z . 



X 



4 THE CACTAC^AS. 



Key to SPKcms. 



A. Flowers large, lo to 20 cm. long. ^ t - n .1 • • . *u- t 



B. Species tall, columnar (except C. pacnyrhtzus] , the joints very thick. 

 Ribs 4 to 6, very high, flat or nearly so (Series i. Hexagonae), 

 Young joints glaucous, blue or bluish green. 

 Spines of young joints short or none. 



Ribs usually 4; young joints light blue i. C. hexagonus^ 



Ribs usually 6; young joints dark blue 2. C, htldmanmanus 



All joints manifestly spiny. ^ , . 



Young spines bright yellow 3. C. alacrtportanus 



Young spines not yellow. 



Flowers red without 4- C. validus 



Flowers green without 5- C. jamacaru 



Young joints not glaucous, green, or sometimes glaucous in No. 7. 



Inner perianth-segments red 6. C. telragonus 



Inner perianth-segments white (unknown in C xanthocarpus). 

 Outer perianth-segments red. 



Spines I to 3, short or wanting or elongated in No. 7; seeds dull. 

 Berry red or orange, unpleasant to the taste 7. C. sienogonus 



Berry yellow, edible. . . , . 8. C. xanthocarpus 



Spines 8 to 13, up to 4 cm. long; seeds shim'ng. 



Tree-like, 6 to 8 meters high, not densely spiny 9. C. lamprospermus 



Lower, I to 3 meters high, densely spiny 10. C. pachyrhizus 



Outer perianth-segments green or brownish. 



Spines few, short or wanting 1 1. C. dayamii 



Spines 6 to 10, up to 10 cm. long 12. C argentincmis 



Ribs 6 to 9, rarely 4, thicker and lower; outer perianth-segments brownish 



(Series 2. Peruvianae) . . * ; 13, C. peruviantis 



BB. Species lower, prostrate, or bushy, the joints mostly not as stout (C. chalybaeus tall). 



Joints green (Series 3. Obtusae), 



Ribs only 4 to 6 mm. high; plants shining 14. C. perlucens 



Ribs much higher; plants dull. 



Spines subulate - 15, f. variabilis 



Flower 20 to 24 cm. long. 



Flower 12 to 16 cm. long 16. C. pcrnambucensis 



Spines acicular. 



Radial spines 5 to 7; central spine i j^^ Q. oblusus 



Radial spines 8 to 10; central spines 4 to 7 , ig, C, caesius 



Joints glaucous blue; species slender (Series 4. Azureae). / ' ' ' • '.' 



Ribs strongly sinuate , ..:.i9. C azure us 



Ribs not strongly sinuate. 



Tree-like; areoles distant. . . , .20. C. chalybaeus 



Bush-hke; areoles close together 21 C aethiops 



AA. Flowers small, 8 cm. long or less; plants columnar (Series 5. Repandae). -•*•••••• 



Flowers 7 to 8 cm, long; spines straight, acicular. 



: Spines up to 5 cm. long, acicular; flowers green; branches constricted ;22. C. rePdndus ' 



; Spmes 2 cm long or less; flowers purple; branches continuous , . . . .23. C. grenadetisis 



Flowers 5 to 6 cm. long; spmes curved, subulate , .....,, . .^4. C margaritetisis 



1. Cereus hexagohus (Linnaeus) Miller, Gard. Diet. ed. 8. No. i. 1768, 



Coc/M5 /t^xagontti Linnaeus, Sp. PI. 466. 1753. , , , ; . - ' 



Cactus odogonus Page in Steudel, Nom. ed. 2. i: 246. 1840. ' ^ ' 



Cereus northumberlandianus* Lambert in Loudon, Gard. Mag. 17: 91. 1841 (FebruarvV 



\ Cereus perrotlehanus Lemaire, Icon. Cact. pi. 8. 1841 to 1847 U eoruaryj. , 



• vSCereM5/«;/>?rfo/pSalm-Dyck, Cact.Hort. Dyck. 1849. 207. 1850. ' 



Plant up to 15 meters high, usually branching near the base, with a trunk 4 dm. in diameter- 

 br^ches usually strict and erect, but in old plants more spreading, made up of short io^ntsTa cm' 

 m diameter or more g aucescent or hght green, usually 6-angled but sometimes 0X4^ or ?-anc.led' 

 occasionally 7 : nbs thin 3 to 5 cm. high, the margins undulate ; areoles abSit 2 cm apart small' 

 felted spines on young branches wantine or few verv short (o t^ ^ r»«. i ^ u ^ apart, small, 



often 8 to ,o or p'erhaps more in a clustlr? ve^'™S„* ^i iXiTlIr? io fi Zt ^''"'T' 

 young brown, but lighter in age; flower 20 to 2^ cm iZi ;tf tSff !i: T ^ *,"""• '°"S' "'''«° 



^ green, short ; |uter pe4th4ment.VnStl^^'^^^^^^^^^^^ 



apiculate, tmged with purple; mner perianth-segments much thinner than goutg- onef,' whke; 



3,8. ,84.) Cereus n,„humberlandi<inus •'^ XX^ Ttl^^?l^^^'kl''^'^''-'T' ''f'l^'^''''- '"''"■ '■- 

 hexagonm. which came from Surinam, leads us to bdicvcthit kffthl™. ■ """^^Tf""" "' L«">Mus's Cactus 

 either C. northumberlandianus or C. fc^u/oliu we here Se it '^ ^""^ "' ""= """"= '= °W" than 



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