1910.] TRELEASE— SPECIES IN AGAVE. 237 



of clear delimitation; and in their essentials they show evidence of 

 being much less mutable than they are commonly supposed to be 

 when judged by the impression that they make on the untrained 

 eye, or when differences in habit are given undue emphasis. 



Explanation of Natural-size Illustrations of Agave Spines. 



Plate XXXII. A, Three spines of Agave americana. B, Three spines 

 of A. picta. C, Three spines of A. sisalana. D, Three spines of A. four- 

 croydes. E, One spine of A. angnstifoUa. 



Plate XXXIII. F-J, Two spines of each of the " zapupe " agaves : F, 

 A. zapupe; G, A. Dezveyana; H, A. aboriginum; I, A. Lespinassei; J, A. 

 Endlichiana. K-N, Spines of Tequila mezcals — two each except the lowest: 

 K, "azul"; L, "ziguin"; ]\I, " mano larga"; N, " Chato." 



