88 MISSOURI BOTANICAL GARDEN. 



The type is specimen No. 8651 D. G., prepared October 2, 

 1908, from cultivated specimens collected March 29, 1907, 

 near Laredo, Texas, under the same collection number. The 

 description is a compilation of two sets of notes, one 

 taken in the type locality and the other beside the culti- 

 vated progeny, supplemented by laboratory studies. — Plate 

 4, upper figure. 



Opuntia caerulescens sp. nov. 



Plant open, loose branching, erect, 10 to 15 dm. high and arborescent in 

 form, with a distinct trunk 5 to 8 cm. in diameter; lateral branches (and 

 fruits) breaking off readily and starting new plants, commonly fow-spined, 

 2.5 to 8 cm. long, or subglobose, and resembling fruits in all but the flower 

 scar, others 1.5 to 3 dm. or more in length and more spiny, the central 

 stem losing all semblance of jointedness, glaucous, dark blue-green, and 

 commonly tinged with copper color on one side, changing irregularly to a 

 dirty gray and epidermis falling off in thin papery shreds in age, tubercu- 

 late with low, not laterally compressed tubercles about 3 mm. high having 

 gradually descending slope below and more abrupt above where the areole 

 is situated, entirely disappearing on old wood; leaves circular in section, 

 subulate, cuspidate pointed, 5 to G or 7 mm. in length; areoles obovate to 

 triangular, 2 to 4 mm. in length on last year's wood, brownish when young 

 but soon turning to a dirty gray, enlarging with age and becoming distinctly 

 sub-areolate; spicules dark reddish-brown, 2 to 3 mm. long, in a compact 

 bunch in upper portion of areole or, at base of some joints, filling the entire 

 areolar area; spines, mostly 1, commonly gray-white at base and reddish- 

 brown distally with sheaths not very loose and dark straw-colored, 1.5 to 

 2 cm. long, with frequently 2 smaller lateral ones and 3 to 4 evanescent, 

 dirty, blackish bristles, not increasing in either numbers or length with age; 

 flowers greenish-purple, about 2 cm. in diameter, witb petals obovate, 

 rounded above, cuspidate pointed, sepals greenish-red, cuspidate pointed, 

 filaments greenish at base, purplish-red above, I to | the length of the 

 style, which is white below, purplish above, 12 to 15 mm. in length, with 

 stigma white or slightly purplish tinged, 4-parted; ovary obovate, 2 to 3 

 cm. long, tuberculate, areolate, bearing circular areoles 1 to 2 mm. in di- 

 ameter and about 6 or 7 mm. apart, beset with abundant bright reddish- 

 brown spicules about 2 mm. in length, proliferous, remaining attached to 

 the plant year after year. 



The species is most closely related to Opuntia Kleiniae, 

 from which it differs in nature and length of spines, color and 

 general appearance of plant body, as well as in the nature of 

 the fruit. The plant has two distinct forms, one more open, 

 fertile, and less proliferous than the other. When grown to- 



