OPUNTIA MACRORHIZA 143 



clearly the one that is illustrated. He is here no doubt following 

 the opinions of Dr. Lindheimer. But it is the upper Guadaloupe 

 plant that is the type of the species and the subsequent errors 

 in interpretation do not affect the case in the least. 



Professor Mackensen collected and studied some of the species 

 of Opuntia on the rocky knolls east of Kerrville in 1909. From 

 his material Dr. J. N. Rose named and figured a tuberous-rooted 

 species in his honor. Professor Mackensen, shortly before his 

 death, informed me that Opuntia Mackensenii is the common, 

 large, tuberous-rooted species of the Kerrville region, and thai: 

 he secured the type a short distance to the eastward from the 



Fig. 2. Two plants of Opuntia macrorhiza under cultivation at Chico, 

 California. 



corporate limits of the town. When I asked for a definite locality 

 the Professor simply remarked that one could not miss it, that 

 it was the conspicuous thing all around Kerrville. 



During the past ten years I have become rather familiar with 

 this region and its species of Opuntia and at present have the most 

 of the forms in cultivation, including material from Professor 

 Mackensen's type collection at Kerrville. The region fr m San 

 Antonio to San Angelo and eastward to Temple and Waco has 

 been frequently visited. Opuntia macrorhiza has been collected 

 at Kerrville, Brownwood, San Saba, Lampasas, Marble Falls, 

 and Leon Springs. The species while variable is not easily con- 

 fused with anything else, and is the most common tuberous- 

 rooted species of the region. 



