166 MISSOURI BOTANICAL GARDEN. 



two of its characters seem to indicate a relationship. The 

 type is yellow flowered, but there are forms which have 

 flowers greenish-yellow, even lighter in color than the flowers 

 of Opuntia leptocaulis. Owing to a constant tendency to 

 segregation of species, it is considered preferable to recognize 

 the yellow flowered form as typical, but I have little ques- 

 tion but that the two forms must be considered specifically 

 the same. The greenish-yellow flowers remain the same 

 color throughout the day, but in the typical form where 

 the flowers are lemon yellow they turn to orange in the aft- 



ernoon, 



d when dried or closed 



specimen 



Corresponding changes in color take place in a large pro- 

 portion of the species of the flat-jointed opuntias. 



d 



f notes made in the type locality when specimens 



collected. 



March 



1910, near Brownsville, Texas, the flowers being collected 



the same plant April 20, 1910.— Plates 19 and 20, 



from 



figure 



Opuntia xanthoglochia sp. nov. 



with 



arms 



over 3 dm. high, but often 8 or 9 dm. in diameter; joints usually wid- 

 est near middle, but sometimes obovate, mostly more or less pointed 

 above and below, about 10 by 15 cm. , dark green, glaucous when 

 young, wrinkled and decidedly raised-tubercular at the areoles; areoles 

 about 4 mm. long, obovate, about 2 cm. apart, enlarging and becoming 

 sub-circular in age, sometimes 1 cm. in diameter; leaves subulate, 

 cuspidate, slightly flattened; spicules light brown when young, but 

 soon turning light yellow, conspicuous and formidable, in compact, 

 4 to 5 mm. long tufts in upper portion of areole, increasing with age, 

 the new ones coming from center of areole and longer from year to 

 vear. the annular growths being in concentric circles, but brown color 



appears 



twisted 



1 or 2, the longest about 2 cm., erect, or when 2 or 3, one sloping 

 downward; flowers lemon yellow, brownish red within, lax, 7 cm. in 

 diameter, turning very light orange to pinkish, filaments greenish, 

 style white, stigma white or very light yellowish, 5 to 6 parted; ovary 

 long, obovate or obconical, somewhat tubercular with raised areoles 

 which are small and sub-circular, about 12 mm. by 6 cm. 



