ILLUSTRATED STUDIES IN THE GENUS OPUNTIA.—Iv. 8] 
raised even when one year old and especially so on young growth, rich 
light to dark velvety brown, becoming dirty brown in age, 4-7 em. 
apart, increasing in size with age; spicules yellow, scattered, unequal, 
1 cm. in length, at first not numerous but soon becoming very numer- 
ous and formidable; spines light yellow, but darker at one year of age, 
annular, flattened, seldom twisted, divergent, 2.5cm. long, formidable, 
2 to 6, mostly about 4 at one year but becoming longer and slightly 
more numerous in age; flowers opening at 7 in the morning, fully opened 
by 8, dark red at first, but changing gradually to deep rich purple on 
exposure, anthers yellow, filaments slightly purplish tinged above and 
greenish below, stigma light green, about-10-parted, style white or 
very slightly tinged; fruit purplish red. 
This is a conspicuous species throughout the delta region 
of the Rio Grande. It is especially conspicuous when in 
bloom. It occurs mostly just above the salt flats where it 
grows with the mesquite, Opuntia gommei?, and O. alta. The 
large, deep, purple flowers and large, more or less wavy, blue- 
green joints are characteristically conspicuous and serve to 
distinguish the species. The shape and character of joint, 
however, vary tremendously with the conditions of vigor 
of the plant. Under ‘cultivation they are much larger and 
more wavy and the margin more likely to be irregular. The 
flowers are difficult to describe. Like so many species of this 
genus a statement regarding the color is of little value unless 
the changes which occur in it after exposure are depicted. 
At first when opening the color is almost brick red with a 
tinge of orange but deeper colored within. Upon exposure to 
the sun the purple color develops very rapidly and in an 
hour the flower is a decided purple. Like all other species 
the opening of the flowers occurs very regularly at a definite 
time of day. 
The description is drawn in the main from a cultivated 
specimen in the third season’s growth, supplemented by notes 
upon native plants in the type locality. This description 
was drawn on the 20th of May, 1911, at Brownsville, Texas, 
when the plants were blooming for the second time that sea- 
son. They had produced one crop of flowers and joints and 
another one-half crop was in bloom from matured current 
year’s growth. This so far as observed does not occur in the 
