1 66 THE CACTACEAE. 



Usually erect, 2 to 4 meters high, with a more or less definite trunk, but at times much lower and 

 spreading; joints green or bluish green, somewhat glaucous, orbicular to obovate, up to 25 dm. long; 

 leaves subulate, 3 to 4 mm. long, somewhat flattened, pointed; areoles distant, often 6 cm. apart; 

 spines usually i to 6, often only 2, one porrect and 4 cm. long or more, the others somewhat shorter 

 and only slightly spreading, pale yellow to nearly white, sometimes brownish or blackish at base, 

 or some plants spineless; glochids yellow or sometimes brownish, usually prominent; petals yellow 

 to dark red; stigma-lobes usually green; fruit purple, pyriform to oblong, 3.5 to 5.5 cm. long. 



Type locality: About New Braunfels, Texas. 



Distribution: Southwestern Louisiana, southeastern Texas, and Tamaulipas, Mexico. 



Opnntia Undheimeri is an extremely variable species, composed of many races, differing 

 in armament, color of flowers, size and shape of joints and of fruit. Certain forms have 

 been described which in cultivation we have been able to recognize as possibly distinct; 

 but in the field they seem to intergrade with other forms, indicating that they are at most 

 only races of a very variable species. In the delta of the Rio Grande this is especially true, 

 and from this region a number of species has been described. In fact, all the plants 

 described as species which are cited above in the synonymy grow within a relatively small 

 distributional area. Dr. Rose has examined all this region and is of the opinion that only 

 one species of this series exists there, and this we believe is to be referred to Opnntia litid- 

 lit'iincri. It is very common about Brownsville and Corpus Christi, where it forms thickets 

 covering thousands of acres of land. It is very variable in habit, being either low and widely 

 spreading or becoming tall and tree-like, sometimes 3 meters high, with a definite cylin- 

 dric trunk. Plants from these two extremes, if studied apart from the field, might be con- 

 sidered as different species, but in the field one sees innumerable intergrading forms. The 

 low, prostrate forms gradually pass into others with more or less erect or ascending branches, 

 while the large tree-like forms often bear large lateral branches which lie prostrate on the 

 ground, indicating that they have developed from the prostrate ones. Decided differences 

 in the flower colors have been pointed out in the original descriptions, and we have observed 

 them in greenhouse specimens, but they do not correlate with other characters. 



Opuntia ellisiana Griffiths (Rep. Mo. Bot. Gard. 21: 170. pi. 25. 1910), an unarmed 

 species, is known only from cultivated plants. Dr. Griffiths states that it is quite different 

 from the Ficus-indicae series, which it much resembles, and is quite hardy in southern Texas. 

 It may be a spineless race of the common 0. Undheimeri of this region. 



Opnntia pyrocarpa Griffiths (Bull. Torr. Club 43: 90. 1916) we do not know; in its 

 long pyriform fruit it suggests this plant ; the type comes from Marble Falls, Texas. 



O. wintcriana Berger and 0. haematocarpa Berger (Bot. Jahrb. Engler 36:455 and 

 456. 1905) are of this relationship, but have browner spines than is usual in the species. 



Opnntia leptocarpa Mackensen (Bull. Torr. Club 38: 141. 1911), characterized by its 

 low, bushy habit and elongated, almost abnormal fruits, suggests a natural hybrid between 

 ( ). Undheimeri and 0. macrorhiza. Indeed, Mr. Mackensen described the species as inter- 

 mediate between these two, and all three species are often found growing together. 0. 

 leptocarpa originally came from San Antonio, Texas. 



Illustrations: Ann. Rep. Smiths. Inst. 1911: pi. 3, 4, B; Cact. Mex. Bound, pi. 75, f. 

 5 to 7; Karsten, Deutsch. Fl. f. 501. 13, i3 a , i3 b ; N. Mex. Agr. Exp. Sta. Bull. 78: pi. [13, 

 14], all as Opuntia ditlcis. Bull. U. S. Dept. Agr. 31: pi. 3, f. i, this as Opnntia cacanapa; 

 Rep. Mo. Bot. Gard. 20: pi. 4, in part, this as Opnntia tricolor; Rep. Mo. Bot. Gard. 20: 

 pi. 9; pi. 13, f. i, these two as Opnntia tcxana. Bull. U. S. Dept. Agr. 31: pi. 2, f. i ; Rep. 

 Mo. Bot. Gard. 20: pi. 2, f. i ; pi. n ; pi. 13, f. 4, all these as Opuntia subannata. Rep. Mo. 

 Bot. Gard. 21: pi. 19; pi. 20, in part, these two as Opnntia alta. Rep. Mo. Bot. Gard. 

 21: pi. 21 ; pi. 22, in part, these two as Opnntia gomei. Rep. Mo. Bot. Gard. 21: pi. 28, this 

 as Opnntia sinclairii. Rep. Mo. Bot. Gard. 22: pi. 9, in part; pi. 10; Journ. Agr. Research 

 4. pi. f., these three as Opnntia cyanclla. Rep. Mo. Bot. Gard. 22: pi. 9, in part; pi. 16, 

 17, these three as Opnntia gilvoalba. Bull. U. S. Dept. Agr. 31: f. i. 



