OPUNTIA. 



67 



pale green, with low, broad tubercles, these elongated and often 4 cm. long or more; leaves linear, 

 10 mm. long or less; spines few, 6 to 10, unequal, the longest ones 2.5 to 5 cm. long, straw-colored, 

 with loose, papery sheaths; flowers purple, 5 cm. in diameter; fruit ovoid, 2.5 cm. long, somewhat 

 spiny or naked; seeds 6 mm. in diameter, irregular in shape. 



Type locality: San Ignacio, Lower California. 



Distribution: Lower California. 



The type of the species is deposited in the Brandegee Herbarium, now a part of the 

 herbarium of the University of California. Living plants have been distributed by A. 

 Berger from La Mortola, Italy, and are now to be found in various collections. 



In the Index Kewensis, first supplement, this species is wrongly entered as Opuntia 

 modesta! 



Figure 82 is from a photograph of a plant sent 

 from La Mortola, Italy, to the New York Botanical 

 Garden in 1913. 



Series 7. FULGIDAE. 

 Much branched, bushy plants, usually with the termi- 

 nal joints very fleshy, the tubercles broad and low, about as 

 broad as long. The species, of which we recognize five, 

 inhabit the southwestern United States and western Mexico. 



Key to Species. 



Joints very readilj' detached, freely falling 30. 0. fulgida 



Joints not very readily detached, persistent. 

 Spines brown or reddish, at least at base. 



Branches slender; fruit not proliferous. ... 31. 0. spinosior 



Branches stout; fruit proliferous 32. 0. prolifera 



Spines white or yellow. 



Spines white; petals greenish yellow, i cm. 



long orl ess 33 



Spines yellow; petals red, 2 cm. long 34 



0. alcahes 

 0. burrageana 



30. 



Fig. 82. — Opuntia molesta. 



Opuntia fulgida Engelmann, Proc. Amer. Acad. 3:306. 

 1856. 



Opunlia mamillala Schott in Engelmann, Proc. Amer. 



Acad. 3 : 308. 1856. 

 Opuntia fulgida mamillala Coulter, Contr. U. S. Nat. 

 Herb. 3 : 449. 1896. 



Plant sometimes 3 meters high or even more, with a 

 rather definite woody trunk 10 to 20 cm. in diameter, 

 much branched, sometimes almost from the base, and 

 forming a compact flattened crown; terminal joints 10 to 

 20 cm. long, 3 to 5 cm. in diameter, very succulent, strongly 

 tuberculate, easily breaking off; spines 2 to 12, yellowish 

 to brown, 2.5 to 3.5 cm. long, acicular, covered with loose, 

 papery sheaths; glochids small, whitish to light yellow; 

 flowers light rose, 2.5 to 3 cm. broad; petals few, obtuse; 



stamens and style very short; fruit at first tuberculate, in age smooth, somewhat pear-shaped, 

 5 cm. long,green, usually very proliferous; seeds rather small, 4 mm. broad, often wanting. 



Type locality: Mountains of western Sonora, Mexico. 



Distribution: Gravelly and sandy situations, southern Arizona, Sonora, and Sinaloa. 



We consider 0. mamillata as synonymous with 0. fulgida; in herbarium and green- 

 house specimens we can find no constant differences. Professor J.J. Thomber, who has long 

 studied this group, says there is no difference between the flowers and fruits, and that there 

 is no difference in distribution (Ariz. Agr. Exp. Sta. Bull. 67 : 501). In the field, however, 

 one can see two rather distinct forms which differ in armament, the typical plant being 

 the more spiny. 



This is one of the most characteristic opuntias of southern Arizona, being very abun- 

 dant on the valley slopes and lower foothills. It often forms dense colonies almost to the 

 exclusion of other cacti, or it may be associated with other species, especially of Opuntia. 



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