144 DAVID GRIFFITHS 



The descriptions of Opuntia macrorhiza^ and Opuntia Macken- 

 senii^ agree very well. In the latter, which seems to be a slight 

 abridgement of a manuscript in Professor Mackensen's hand, it 

 is stated that the flowers are yellow, in the former yellow with 

 reddish base. This latter condition is described in Professor 

 Mackensen's manuscript as ''light reddish-brown centered." 

 There is some confusion in words as to the fruit but that might 

 easily have occurred. In the original description of Opuntia 

 macrorhiza no mention is made of the exterior color of the fruit, 

 but later^ Dr. Engelmann, evidently from the same material, 

 adds that the fruit is green or pale-purple, which has no contra- 

 diction of "rose-purple with a nearly colorless, pleasant-tasted 

 pulp" which is predicated of Opuntia Mackensenii. This state- 

 ment is exactly that of Mackensen's manuscript description. A 

 copy of my own notes on this point, taken from cultivated speci- 

 mens from Kerrville, are as follows: 'Fruit a rather light pur- 

 plish-red with bloom remaining through early maturity, rind 

 greenish and pulp colored a little — rather mottled." 



To summarize, there is clear evidence, both descriptive and 

 geographical, that the common tuberous-rooted Opuntia of the 

 rocky knolls between the Guadaloupe and the Pedernalis (Pic- 

 cardinales, Pierdenalis) is Opuntia macrorhiza; that the figures 

 in Plate 69 of the Cactaceae of the Mexican Boundary Survey 

 pertain to an entirely different species ; and that Opuntia Macken- 

 senii is synonymous with Opuntia macrorhiza. 



The true Opuntia macrorhiza has not been treated by me here- 

 tofore in any of my publications. In one case^ the name was 

 erroneously applied to what has since been, in part at least, 

 named Opuntia leptocarpaJ 



There still remains the task of accounting for the plant figured 

 in Plate 69 of the Cactaceae of the Mexican Boundary Survey. 

 But this is another and very different story which will be treated 

 later. 



3 Boston Jour. Nat. Hist. 6: 206. 1850. 

 *Contr. Nat. Herb. 13: 310 1911. 

 5 Proc. Amer. Acad. Arts and Sci. 3: 296. 1856. 

 « New Mex. Coll. Agr. Bull. 60: 58-59. 1906. 

 7 Bull. Torr. Bot. Club. 38: 141-142. 1911. 



