260 PROCEEDINGS OF THE AMERICAN ACADEMY 



" The Pacific Railroad expeditions since 1853 have opened fields not 

 before explored ; and Dr. Bigelovv, the botanist and physician of Cap- 

 -tain A. W. Whipple's expedition along the 35th parallel, availed him- 

 self of these opportunities in a most successful manner ; while Dr. 

 F. V. Hayden, almost unaided in his adventurous expedition, has ex- 

 tended our knowledge of the northernmost Cactaceaj in the regions of 

 the Upper Missouri and Yellowstone Rivers. 



" The last, but by no means least addition, was made in 1854 and 

 1855, by ]VIr. Arthur Schott, during the exploration under Major 

 Emory of the country south of the Gila River, known as the Gads- 

 den Purchase. 



" Most of the materials brought together by these different explorers 

 have come into the hands of the writer ; but few of the discoveries 

 made since 1847 and 1848 have been given to the public ; — partly 

 . because the material on hand very often was incomplete, and partly 

 because it seemed desirable to publish the whole in an elaborate form 

 with the Reports of the Boundary Commission and those of the Pacific 

 Railroad Surveys. These reports are now in preparation ; but the 

 splendid plates which are to illustrate the natural history of these 

 plants cannot be finished for some time ; it is therefore deemed ad- 

 visable now to publish short descriptions of the new species, and sys- 

 tematically to arrange them with those before known. 



CACTACE^. 



Tribus I. TUBULOS^, Miquel. 



Subtrib. 1. Parallels. Cotyledones margine hilum versus spec- 

 tantes, lateribus seminis parallelae. 



I. MAMILLARIA, Haw. 



Ovarium baccaque Iceves. Semina fere exalbuminosa. Cotyledones 

 abbreviatae, plcrumque erectaj, subconnatce. — Plantse mamillato-tu- 

 borculatee ; inflorescentia laterali s. verticali. 



Subaen. 1. Eumamillakia. Flores ex axillis tuberculorum anni 

 prioris nunquam sulcatorum : ovarium plerumque immersum versus 

 fructus maturitatem emergens. 



<^ 1. PoJyacanthoi, Salm. 



1. M. MiCROMERis, E. in Bound. Comm. Rep. : parvula, simplex, 

 globosa ; tuberculis minimis verrucffiformibus confcrtissimis ; areolis 



