— 336 ~ 



Eucif/ave. 



End spine decurrent for a considerable distance (Snbinarffinatae). 



Leaves long, thick, concave, upciirved, long-attenuate, rather evenlj'- 

 toothed I. afrorireiis. 



Leaves broad, thinner, convex in the niiddle, recurved, acnte, very 



repandly and unevenly toothed 1. Hookeri. 



End spine not or scarcely decnrrent on the leaf niargin. 



Leaves thick and fleshy, elongated, niostly recnrving at end, gray-glaucons 



{Amerieanae). 



Spine stout, recurved (1 : 4 or 5} .4. amerirana. 



Spine siender, straight (1 : 10) I. picta. 



Leaves thinner but fleshy, broad, typically upcurved at end, green 



{^SoboliferaeY). 



Variegation green-yellow A. sohoUfera. 



Variegation bright yeliow Ä. Morrisü. 



Leaves fibrous when mature, stiffiy spreading {liigulae). 



Leaves very long, gray, slightly repand: stem tall . .1. fourcroydes. 

 Leaves short, greener, not repand : low A. angustifolia. 



Littaea. 



Leaves soft-fleshy, at most papery-margined : prickles very small and 

 crowded .L albicans. 



Leaves fibrous, horny-margined {Marginatae). 



Smooth, prickles rather smali A. lophanfha. 



Rough on back, prickles very iarge 1. .ii/Ioinicaiitha. 



The foilowing key may serve to differentiate the foims, prima- 

 rily by their variegation characters: — 



Yariegatiou niarsrinai. 



Leaf vvithoutend spine, at most with a short button. Fnrcrata Sc/Ion marginaia. 

 End spine present (Asrave). 

 Leaves not horny-margined. 

 Leaves fleshy. often concave. 



End spine long-decurrent: leaves upcurved 



at end .t. atrorimiti niarginata. 



End spine little if at all decurrent. 



Leaves glaucous, gray, narrow, mostly recurved at end. 



Spine Short and stout A. amcriania marffinafa. 



Spine siender A. picta. 



Leaves deep green, broader, typically upcurved at end. 



Variegation greenish 1. aololifcra morginata. 



Variegation yeliow I. Morrisü niarginata. 



') Tliough apparently offering flower, fruit or panicie differentials, the 

 species of this group seem scarcely separable as yet by foliage characters. 



