ROSE — MEXICAN AND CENTRAL AMERICAN PLANTS. 311 



the bristles becoming yellowish in age, the lower areoles naked, the upper bearing 

 1 to 4 unequal spines; spines brown, white, or brown below and white above, all 

 becoming gray or whitish in age, mostly flattened on one side and twisted, slender, 

 on young joints spreading, on very old ones usually reflexed; flowers medium-sized, 

 yellow, with a 7 or 8-lobed stigma; fruit spineless, oval (or sometimes narrower with 

 or without a contracted base), 4 to 5, rarely 6 cm. long, truncate at apex, rose-purple, 

 with a nearly colorless, pleasant-tasted pulp; seeds suborbicular, 5 to 6 mm. broad, 

 acutish- margined, nearly white. 



Type U. S. National Herbarium no. 617434, collected by Bernard Mackensen, near 

 Kerrville, Texas, August, 1909. The photograph was taken in Washington. 



The following note by Mr. Mackensen made in the field is of considerable interest: 



I now send you two more packages containing more typical specimens of 0. macken- 

 senii. I am also trying to have a photograph made of a large, :ypical plant. I have 

 had to revise my ideas of this species somewhat in consequence of the examination of 

 numerous specimens growing under various conditions. I find that many plants are 

 without tubers, and I believe this to bo the case especially with those produced by 

 vegetative propagation. On normal plants the fruit is oval and rose-purple; on those 

 suffering from drouth, disease, etc., it is usually narrower and frequently contracted 

 below. 



Opuntia mackensenii differs from . ferruginospina chiefly in its tuberous roots and 

 procumbent habit, and in the shape and size of its joints, character of its spines, yellow 

 color of its flowers, size, shape, color, and taste of its fruit, and size and color of its 

 seeds. It is evidently more closely related to 0. macrorhiza, from which it differs 

 chiefly in the size of its joints and the number and character of its spines, in its 7 or 

 8-lobed stigma, and in the form and color of its fruit. 



APIACEAE. 

 A NEW ARRACACIA AND A NEW ERYNGITTM. 



Arracacia compacta Rose, sp. nov. 



Perhaps a meter high; stems purplish, more or less glaucous; basal leaves 35 cm. 

 or more long, ternately compounded; ultimate segments lanceolate, sometimes lobed 

 below, sharply serrate, acute, glabrous above, pubescent beneath; ultimate peduncles 

 rather short, 2 to 4 cm. long; involucral and involucel bractlets wanting; peduncle 

 1 cm. or less long, pubescent when young; pedicels short, puberulent; flowers appa- 

 rently purplish; fruit abundant, forming large compact heads hiding the peduncles 

 and pedicels; carpels 12 to 14 mm. long, glabrous, sharply ribbed, with slender style 

 but no stylopodium; ribs nearly equal, broad at base, acute; old tubes one in each 

 interval and one under each rib; seed in cross section showing a deep concave base, 

 the outer margin corrugated . 



Type U. S. National Herbarium no. 592478, collected by Dr. C. A. Purpus at an 

 altitude of 2,100 to 2,400 meters on Cerro de Chicamole, Puebla, Mexico, August, 1909 

 (no. 4110). 



I have referred this species tentatively to Arracacia, although it lacks the stylopo- 

 dium of that genus. 



Eryngium purpusii Hemsley & Rose, sp. nov. 



Perennial; stem rather slender, 60 to 80 cm. long, glabrous, naked below the inflo- 

 rescence; basal leaves numerous, 20 to 35 cm. long, about 12 mm. broad, with numer- 

 ous spinescent linear lobes narrower than the breadth of the leaves, often bearing 

 small prickles in the axils of these lobes; inflorescence a terminal umbel somewhat com- 

 pounded together with several axillary clusters; heads 2 cm. cr more long, longer than 

 broad; bracts erect, entire, pungent, 8 to 12 mm. long; bractlets entire, pungent; 

 styles elongated; carpels naked below but bearing a few ovate scales above. 



Type U. S. National Herbarium no. 592477, collected by C. A. Purpus on Cerro de 

 Cacalotl, Puebla, Mexico, August, 1909 (no. 4109). 



