OF ARTS AND SCIENCES. 291 



O. Lindheimeri, E. PI. Lindh., is partly this same plant, partly a 

 hybrid form between it and perhaps O. Rafinesquii, with narrow 

 clavate fruit. 



O. Engelmanni, var. ? cyclodes, E. & B. in P. R, E,. : articulis 

 orbiculatis ; aculeis validioribus subsingulis ; bacca parva globosa ; 

 seminibus majoribus. 



On the Upper Pecos, in New Mexico. Joints 6-7 inches, and 

 fruit 1 or 1^ inches in diameter. 



O. DTJLcis, E, in B. C. R., is a doubtful plant, of which we have 

 not material enough. It has been found near the middle course of 

 the Rio Grande, near Presidio del Norte, &c. It is similar to O. En- 

 gelmanni, and may be a form of it ; but it is lower, more spreading, 

 with a similar but very sweet fruit, and small, regular seeds. 



The following may be considered as a subspecies : — 



O. occiDENTALis, E. & B. in P. R. R, : erecta, patulo-ramosissima ; 

 articulis grandibus obovatis vel rhomboideis ; pulvillis remotis setas 

 graciles confertas et aculeos 1-3 validos compresses deflexos albidos 

 basi obscuriores et inferiores paucos graciliores gerentibus ; floris 

 flavi intus rubelli ovario obovato ; bacca obovata late umbilicata ; se- 

 minibus majoribus. 



On the western slope of the California mountains, near San Diego 

 and Los Angeles : fl. June. — Plant 4 feet high, forming large thick- 

 ets ; the joints 9-12 inches long ; pulvilli with very fine closely-set 

 bristles ; spines about one inch long. Apparently distinct from 0. 

 Engelmanni by its manner of growth, the very fine bristles, and the 

 larger seeds. 



There are also some indications of another form, growing on hills 

 and plains near San Diego, California, and on the neighboring sea- 

 beach, with higher and more upright growth, and coarser bristles 

 on the pulvilli, but which I cannot well distinguish from 0. Engel- 

 manni. I have seen no fruit or seed of it. 



6. O. CHLOROTicA, E. & B. in P. R. R.: caule erecto aculeis flavis 

 numerosissimis fasciculatis armato ; articulis orbiculato-obovatis palli- 

 dis ; pulvillis subremotis setas difformes confertas aculeosque 3-6 in- 

 sequales compresses stramineos gerentibus ; floris flavi ovario pulvillis 

 confertis stipato ; petalis spathulatis. 



Western Colorado country, between New Mexico and California, 

 from the San Francisco mountains to Mojave Creek. — Plant 4-6 

 feet high, forming large and sometimes spreading bushes ; the trunk 



