OF ARTS AND SCIENCES. 265 



Var. /3. c^spiTOSA (M. similis, E. in PI. Lindh. 1845) : csespitosa ; 

 aculeis radialibus 12 - 15 puberulis, central! plerumque deficiente ; 

 llpribus baccis seminibusque majoribus ; stigmalibus 5 patulis. 

 ; Var. y. robustiok, E. in PI. Lindh. 1850 : subsimplex ; tuberculis 

 longioribus laxioribus, aculeis robustioribus Icevibus, radialibus 10-12, 

 centrali singulo ; floribus majoribus ; stigmatibus 7-8 patulis ; semini- 

 bus ut in /3. 



Plains east of the Rocky and New Mexican Mountains. Var. a. on 

 the Upper Missouri ; /3. from Kansas River to New Braunfels in Texas ; 

 y. from the Canadian River to the Colorado of Texas. The heads 

 are one or two inches in diameter ; the csespitose masses of /3. often a 

 foot broad ; spines 3-8 lines long. Flowers 1-2 inches long and 

 wide, of a greenish or reddish or pure pale yellow color. Seeds 

 0.8- 1.1 lines in diameter, more regularly globose than in most other 

 Cactacse. 



16. M. ScHEERii, Muhlenpf. 1847 ; /3. ? valida, E. in B. C. R. : 

 magna, ovato-globosa, subsimplex, glaucescens ; tuberculis remotis 

 patulis magnis e basi lata subcylindricis supra sulco profundo glandu- 

 lis paucis munito (juniore lanato) subbilobis ; areolis junioribus dense 

 lanatis ; aculeis 10 - 20 rectis robustis basi bulbosis albidis s. citrinis 

 apice fuscatis, radialibus 9 - 16 ; centralibus 1-5 validioribus angu- 

 latis ; floribus flavis ex axillis junioribus tomentosissimis. 



Sandy ridges in the valley of the Rio Grande near El Paso : fl. 

 July. The largest of our Northern Mamillarice, 7 inches high and 5 

 in diameter; tubercles 1-1| inches long; spines 10-18 lines in 

 length, very stout, especially the central and lower radial ones. 

 Flower 2 inches long, yellow. Fruit not seen. — M. Scheerii from 

 Chihuahua, according to Prince Salm's description, is a smaller plant, 

 with single central spines one inch in length, and 8-11 much shorter 

 radial spines ; the areolse are described as naked : — nevertheless our 

 plant is probably only the northern form of this species. 



17. M. KOBUSTisPiNA, A. Schott, in litt. : simplex s. cffispitosa ; 

 tuberculis patulis teretibus magnis sulcatis ; areolis junioribus dense 

 tomentosis ; aculeis radialibus 12 - 15 robustis inferioribus robustiori- 

 bus ssepe curvatis, superioribus rectis fasciculatis paullo tenuioribus, 

 centrali singulo valido compresso recurvato, omnibus subpollicaribus 

 cornels apice atratis ; floribus luteis ex axillis junioribus tomentosis- 

 simis ; seminibus magnis obovatis fuscis Isevibus. 



Sonora, on grassy prairies : fl. July. Tubercles nearly an inch 

 VOL. III. 34 



