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52 



TH^ CACTAC^A^. 



^hr>rt f -> to 6 cm lone) • arcoles on old stems bearing 3 or 4 long (2 to 4 cm. long) needle-like brownish 

 h s^ynm^ with a single spine ea?h, filled with brown wool; glodnds brown, numer- 



ous sheaths on young spine J straw-colored, soon deciduous; flowers and fruit unknown. 



Description based on field notes and on living and herbariutn specimens 

 rollectedbvDr.Rose on Santa Cruz Island, Gulf of Calif ornia, April i, 1911 (No. 16845). 



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Opuntia sp. 



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Procumbent, forming an indeterminable mass of spiny branches, 3 to 10 dm. in diameter; old 

 stemiwooTy smi^oth. bro'wn, and shiny, 2 cm in diameter; branches - ^^ ^ cm^ long blu^^^^^ 

 spines of two kinds; the 2 to 4 principal ones long (2 to 3 cm. ^^^^l ^^^^^^'l^^^'f^^^^ 

 thin yellow sheaths, straw-colored when young, becommg purplish finally fading to gray, secondary 

 spines 4 to 6, radial, inconspicuous; glochids brownish; flowers and fruit unknown. 



4 



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herbarium specimens 



Collected by Dr. J. N. Rose on East San 



March 



1911 



(No. 16085). This is, doubtless, the plant referred to by Walton 



J 



137- 1899) 



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Series 3. THURBERIANAE. 



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J 



Bushy, arborescent, or depressed species, with slender joints, the ultimate ones tuberculate, 

 about 2 cm. thick or less, the areoles bearing several spines. We recognize 8 species, 7 of them 



Mexico 



Key to Species. 



r 



P 



Bushy or arborescent species, 6 dm. high or higher. 



Tubercles narrowly oblong, i cm. long or more. ^ vivipara 



Joints readily detached ^ 



Joints not readily detached. 



Longer spines 2.5 cm. long or longer. • tetracanlha 



Flowers orange to scarlet 9 ^^-^^ 



. Flowers purple ^ 



^ 



^ 



Spines 2 cm. long or less 



O. thurberi 



I 



opuics ^ «-iii. •Wits "1 ■•-^•' J-, n rlnvdlina 



Tubercles low. oblong, 6 to 8 mm. long ^2. C. ciaveuma 



Depressed species, 6 dm. high or less. . , • , „ 



Spines yellow or brown; flowers green or tmged with yellow. n ^ • « 



Spines yellow, up to 5 cm. long; petals i to 1.5 cm. long ^3- (^- aavisn 



Spines brown, 2.5 cm. long or less; petals 2 to 2.5 cm. long H- )!!■ ^%\^J{^,."' 



Spines white; flowers yellow '5- O- wUpplet 



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\ 8. Opuntia vivipara Rose, Smiths. Misc 



1908. 



Plant 2 to 3.5 meters high, usually several strong branches from the base, 8 to 10 cm. in diame- 

 ter, much branched above, but not compactly so ; old stems with rather smooth bark ; young branches 

 bluish green, slender, i to 2 cm. long, 10 to 12 mm. in diameter; tubercles low, oblong, 15 to 20 mm. 

 long ; areoles when young bearing a dense cushion of yellow wool with few or no glochids ; spines 

 I to 4, 2 cm. long or less, porrect or ascending, covered with straw-colored sheaths ; leaves small, terete. 



■*", 



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borne 



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strondv tuberculate, bearing white deciduous bristles; fruit oblong, 4 to 6 cm. long, smooth, with a 



yellowish green, spmeless; seeds white, very thick, 5 mm 





Type locality: Near Tucson, Arizona. 



Disin6wa"ow.- Known only from type locality. 



The relationship of this species is doubtful; it resembles certain garden forms of 





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from tvDical forms of that species in its much 



seeds, different armament, and habit. 



spinosio 



and 



O. versicolor, but there is no indication that it is the result of hybridization of those species 



Illustrations: Smiths. Misc. Coll. 52: pi. 12; 



Plate VII, figure 2, represents a branch 



World 

 L. C. C. Krieger at the Desert 



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Labo 



Tucson, Arizona; 



figu 



I, 



from a photograph of 



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the type plant taken by Dr. MacDougal 



1908. 



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