STANDLEY TREES AND SHRUBS OF MEXICO. 113 



Leaves with pungent short spine. 



Leaves not denticulate 129. A. vilmoriniana. 



Leaves minutely denticulate 130. A. pedunculifera. 



GCG. Leaves with evident spine and teeth. 

 Spine and teeth soft and weak or small. 



Leaves glaucous or gi'een. Teeth more or less irregularly connate. 



131, A. celsii. 



Leaves gray-green. Teeth mostly distinct 132. A. micracantha. 



Leaves green, with pale median stripe 133. A. pendula. 



Spine and teeth firm and relatively large. 



Teeth close together; leaves green 134. A. polyacantha. 



Teeth more separated (10 mm. apart) ; leaves commonly glaucous. 



Flowers yellowish white, moderate 135. A. xalapensis. 



Flowers deep yellow, large (75 mm. long) 136. A. macrantha. 



BB. Leaves with soft dry border, spine, and teeth 137. A. pumila. 



BBB. Leaves with detachable hoi'ny border and with pungent spine. 

 D. Leaves falcately ascending, thin, not repand. 



Leaves green or bluish 138. A. lecheguilla. 



Leaves gray-green, somewhat glaucous 139. A. funkiana. 



DD. Leaves spreading, rather narrow and thin, repand. 



140. A. lophantha. 

 DDD. Leaves spreading, rather broad and usually thick. 



Leaves relatively thin, without pale ventral stripe 141. A. horrida. 



Leaves thicker. 



Leaves usually with pale ventral stripe 142. A. roezliana. 



Leaves without pale ventral stripe. 



Leaves fleshy, incurved 143. A. ghiesbreghtii. 



Leaves fibrous, straight 144. A. obscura. 



DDDD. Leaves often falcate, ascending, thick and stilf. 

 Spine short (25 mm. long). 



Teeth long (5 to 15 mm.) if widely .separated 145. A. triangularis. 



Teeth scarcely 5 mm. long, distant 146. A. potrerana. 



Spine long (over 50 mm. long). Spike very dense 147. A. kerchovei. 



DDDDD. Leaves spreading, oblong, thin, or else fieshy rather than hard. 

 Horny margin of the leaf continuous. 

 Teeth not on green hummocks. 



Leaves gray-green or blue-green, rather few — 148. A. inopinabilis. 

 Leaves light green or glaucous. 

 Leaves light green, scarcely glaucous. 



Spike very compact 149. A. convallis. 



Spike rather loose 150. A. expatriata. 



Leaves glaucous. 



Leaves flaccidly recurved 151. A. dissimulans. 



Leaves not recurved 152. A. angustiarum. 



Teeth saddling fleshy hummocks. 



Leaves rough. Teeth very broad 153. A. xylonacantha. 



Leaves smooth. 



Teeth mammaeform 154. A. washingtonensis. 



Teeth triangular 155. A. splendens. 



Horny margin interrupted in the middle 156. A. vittata. 



DDDDDD. Leaves straight, 3-edged. very hard 157. A. victoriae-reginae. 



BBBB. Leaves with (characteristically) detachable marginal threads, and 

 with pungent spine. 



