200 



THE CACTACEAE. 



polyacantha microsperma and 0. polyacaniha ntfispiim, mentioned in Bailey's Standard 

 Cyclopedia of Horticulture (3: 2363. 1916), belong here. 



Opuntia polyacantha was one of the first of our western opuntias to be collected and 

 described. It was first collected by Thomas Nuttall on his memorable trip to the Upper 

 Missouri. He described it in 1818 as Cactus ferox, a name which had been previously used 

 by Willdenow, which led A. H. Haworth in 1819 to rename Nuttall's plant, calling it Opun- 

 tia polyacantha. At the same place Haworth published a second name, Opuntia media, 

 undoubtedly based on a less spiny form of O. polyacantha. In 1828 Nuttall's plant was 

 again renamed, this time by A. De Candolle, who called it Opuntia missouriensis, under 

 which name it was known for many years. In 1896 Dr. John M. Coulter very properly 

 restored Haworth's name 0. polyacantha. 



This species has a wide distribution laterally and altitudinally. It is properly a 

 plains' species, but is found in mountain valleys and on dry hills, usually in the open, 

 but sometimes in sparse pine woods. In a species of such wide distribution and growing 

 under such diverse circumstances, a wide range of forms is to be expected and a number of 

 varieties have been proposed for the various races, some of which may perhaps have red 

 flowers. The plant is hardy at New York, flowering freely in June. 



Illustrations: Curtis's Bot. Mag. 115: pi. 7046; Illustr. Fl. 2: f. 2531 ; ed. 2. 2: f. 2990; 

 N. Mex. Agr. Exp. Sta. Bull. 78: pi. [3]; Cact. Journ. i: 167; Card. Chron. 50: 340, the last 

 two as Opiuitia missouriensis; Pac. R. Rep. 4: pi. 14, f. 8 to 10; pi. 23, f. 18, the last two as 

 Opuntia missouriensis albispina; Pac. R. Rep. 4: pi. 14, f. 5 to 7; pi. 24, f. i, 2, the last two 

 as Opuntia missouriensis microsperma; Pac. R. Rep. 4: pi. 14, f. 4; pi. 23, f. 17, these last 

 two as Opuntia missouriensis platycarpa; Pac. R. Rep. 4: pi. 14, f. i to 3; pi. 23, f. 16. these 

 last two as Opuntia missouriensis nifisphia: Monatsschr. Kakteenk. 9: 148, this last as 

 Opuntia schwcriniana. 



Plate xxxv, figure 3, represents 

 a flowering joint of the plant collected 

 by Dr. Rose in western Kansas in 

 1912. Figure 247 represents joints 

 of the plant from Colorado, photo- 

 graphed by T. W. Smillie. 



Series 24. STENOPETALAE. 



This is an anomalous group in 

 Opuntia, since the flowers are dioeci- 

 ous and the petals are linear and more 

 or less erect. It contains three species 

 which are very different in habit and 

 color of spines, but which were all 

 united into a single species by Profes- 

 sor Schumann. Dr. Engelmann was so 

 much impressed by the peculiar struc- 

 ture of the flowers of this group that he 

 proposed for it a new subgenus, Sic no- 

 punt ia. 



KEY TO SPECIES. 



Spines dark; plants low, 



prostrate 225. 0. stenopetala 



Spines white; plants erect. 

 Joints narrow; spines 



acicular 226. 0. glaucescens 



Joints broader; spines 



stouter 227. O. grandis 



225. Opuntia stenopetala Engelmann, Proc. Amer. Acad. 3: 289. 1856. 



Low bushy plant, often forming thickets, the main branches procumbent and resting on the 

 edges of the joints; joints obovate to orbicular, i to 2 dm. long, grayish green, but often more or less 



FIG. 248. Opuntia stenopetala. 



