OF ARTS AND SCIENCES. 299 



stigmatibus 8 in capitulum congestis ; bacca obovata late umbilicata 

 (sicca ?) ; seminibus magnis crassis subregularibus. 



On Williams's River, the Colorado, and the Mojave, and down to 

 the Gila : ■ fl. April and May. — Habit very different from any other 

 of our Opimtice ; the stout obovate or fan-shaped joints (5-8 inches 

 long) originate from a common base, forming a sort of rosette. 

 Leaves only one line long, 4-6 lines apart; pulvilli red-brown, 

 somewhat immersed. Flower about 2| inches in diameter ; ovary 

 with 40 - 60 pulvilli. Fruit apparently dry, thereby approaching the 

 next section. Seed 3 lines in diameter, 2 lines thick. 



Mr. Schott has observed, on the dividing ridge of the California 

 mountains, west of the mouth of the Gila, and again in the Santa 

 Cruz Valley, Sonora, a very similar but suberect species, 3 feet 

 high, spineless, inclined to assume a purplish hue, which he seems to 

 have confounded with O. hasilaris. Can it be 0. riijida, or is it an 

 undescribed species ? 



§ 6. Xerocarpece : diffusce : articuli suborbiculati vel tumidi : aculei 

 plurimi : bacca sicca aculeolata : semina eburnea, magna, plerum- 

 que latissime marginata. 



*"" Articuli compressi siiborhiculati. 



22. O. HysTRiciNA, E. & B. 1. c. : diffusa ; articulis obovato-orbi- 

 culatis ; pulvillis subconfertis setas pallidas rutilasve gerentibus, omni- 

 bus armatis ; aculeis 5-8 superioribus validis elongatis angulatis seu 

 tortis patulis vel deflexis, inferioribus 5-7 gracilioribus radiantibus ; 

 bacca ovata aculeolata, umbilico planiusculo ; seminibus maximis. 



West of the Rio Grande, to the San Francisco mountains. — Joints 

 3-4 inches long ; pulvilli 5-6 lines apart, unusually large ; longer 

 spines 1| - 3 and even 4 inches long, brownish ; lower radiating ones 

 white, 4-9 lines long. Fruit an inch long ; upper pulvilli with 4-6 

 bristly spines. Seeds 3i lines in diameter, among the largest in this 

 genus. 



23. O. MissouRiENSis, DC. (Cactus ferox, Nutt. Gen.) : prostra- 

 ta ; articulis obovatis vel suborbiculatis tuberculatis ; foliis minutis ; 

 pulvillis subconfertis stramineo-setosis, omnibus armatis ; aculeis 5 - 

 10 exterioribus radiantibus setiformibus albidis, 1-5 inferioribus ro- 

 bustis albidis seu rufescentibus ; floris flavi intus aurantiaci ovario obo- 

 vato vel subgloboso spinuloso ; stigmatibus 5-10 viridibus ; bacca 

 spinosa, umbilico piano ; seminibus magnis irregularibus. 



