192 



THE CACTACEAE. 



Berger remarks that this species is very variable, but that it can not well be divided 

 even into varieties. 



Opiintia megalarthra Rose (Smiths. Misc. Coll. 50: 529. 1908), in its very spiny joints, 

 yellow spines, and small fruits, seems very different from the common cultivated O. robusta; 

 yet when grown in the greenhouse for several years it takes on much the appearance of 

 0. robusta. If this view is correct, 0. megalarthra represents the wild form of the species. 



Opuntia cochinera Griffiths (Rep. Mo. Bot. Gard. 19: 263. pi. 26. 1908) from Zacatecas, 

 Mexico, is, perhaps, a hybrid between Opuntia robusta and one of the Sircptacantkae. 



Illustrations: N. Mex. Agr. Exp. Sta. Bull. 60: pi. 5, f. i; Monatsschr. Kakteenk.23: 

 135; Joum. Inter. Gard. Club 3: 14, the last two as Opuntia gorda; U. S. Dept. Agr. Bur. 

 PI. Ind. Bull. 74: pi. 5, as Tapuna pear. ? N. Mex. Agr. Exp. Sta. Bull. 64: pi. i. 



Plate XXXIV, figure 4, represents a joint of the plant collected by Dr. Rose in Hidalgo, 

 Mexico, in 1905, and described by him as Opuntia megalarthra. Figure 238 is from a photo- 

 graph taken in Zacatecas, Mexico, by Professor F. E. Eloyd in 1908. 







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Fig. 238. — Opuntia robusta. 



214. Opuntia guerrana Griffiths, Rep. Mo. Bot. Gard. 19: 266. 1908. 



Plant 9 to 12 dm. high, with an open, branching top; joints oblong to orbicular, 15 to 25 cm. 

 long, thick, glaucous; areoles 5 mm. in diameter, filled with tawny wool; spines white to yellow, 

 I to 6, flattened, twisted; petals yellow; filaments greenish white; stigma-lobes green; fruit globose 

 greenish white, 4 to 5 cm. in diameter. 



Type locality: Near Dublan, Hidalgo, Mexico. 

 Distribution: Known only from type locality. 



Except in size and color of fruit this species is very much Uke the common Opuntia 

 robusta of this part of Mexico. 



215. Opuntia fusicaulis Griffiths, Rep. Mo. Bot. Gard. 19: 271. 1908. 



Plant 5 meters high or less, the branches erect or spreading; joints oblong, elongated, 4 dm. 

 long or less, much longer than wide, glaucous, bluish green, spineless, narrowed at both ends; glo- 

 chids often wanting; areoles small, filled with tawny wool; fruit greenish white. 



Type locality: Described from cultivated plants. 

 Distribution: Known only from cultivated specimens. 

 Illustration: Rep. Mo. Bot. Gard. 19: pi. 23, in part. 



