ILLUSTRATED STUDIES IN THE GENUS OPUNTIA — H. 87 



gether under cultivation the two forms are indistinguishable, 

 although quite different in habit in their natural habitat. 



The type is No. 7632 D. G., prepared from a cultivated 

 specimen April 23, 1908. The original material was collected 

 at San Luis Potosi, Mexico, March 12, 1905. The description 

 is a compilation of a partial description written in the type 

 locality and a more complete one made in the field, of the culti- 

 vated, mature, three-year-old plant, supplemented by studies 

 of the living material in the laboratory.— Plates 6, upper fig- 

 ure; 2, f. 9 



Opuntia gilvescens sp. nov. 



Plant low, prostrate to slightly ascending -mth main branches on edge 

 on ground and secondary ones short, erect or ascending from them, 7 to 8 

 dm. high and about 12 dm. in diameter, loosely branched and symmetrical 

 with main branches usually 3 or 4, radiating in all directions; joints obo- 

 vate, very pale, smooth, glossy, glaucous green changing to a light yellow- 

 green not later than beginning of second year, commonly 20 by 25 cm. 

 but mostly smaller and 12 to 16 mm. thick; areoles obovate, about 4 to 5 

 mm. in longest diameter, tawny-yellow, enlarging in age to subcircular 

 and often becoming 6 or 7 mm. in diameter, 3 to 4.5 cm. apart; spicules 

 always yellow, mostly about 4 mm. long, nearly or quite surrounding the 

 darker tawny wool, but more abundant above, increasing in age to 9 or 

 10 mm. in length, mostly in more or less plainly distinguishable concentric 

 circles, the new ones being inside of the old, which become dirty yellow, 

 the marginal areoles completely and compactly filled with spicules after 

 first year, marginal ones more loosely and unequally arranged; spines not 

 numerous, at first translucent, soon becoming bleached white distally 

 with dark bases, and with age changing through flesh-color to chalky 

 white throughout, or the bases may remain somewhat tinted, tips always 

 translucent, 1 or none to 4, mostly less than 2.5 cm. in length the first year, 

 but sometimes even 4 cm. , increasing in age to as many as 6 and somewhat 

 longer also, erect, divergent, but sloping downward slightly in age, flat- 

 tened, annular, seldom twisted; flowers yellow; fruit a light, glossy red 

 with often a tinge of purple below, rind greenish and pulp lighter green, 

 obovate, its areoles about 1.5 to 2 cm. apart, tawny, permanently yellow 

 spicular; seed flattened, irregular, angular, 4 or 5 mm. in diameter, with a 

 prominent, rounded, irregular roughened marginal caUus about 1 mm. in 

 width, narrowing toward the prominently notched hilimi. 



The species belongs to the 0. phaeacantha group but differs 

 from that species in its many variations in being a larger 

 jointed plant, being lighter and more glossy in color, and de- 

 cidedly different in the nature and number of its spines. It 



