326 PROCEEDINGS OF THE AMERICAN ACADEMY. 
perhaps confluent with this species are the plants referred by Dr. Gray 
to his MM. borealis var.? Texana, Pl. Wright, i. 61 (Wright no. 159, 
also no. 10, coll. of 1851, and Gregg, no. 51). They differ from MM. 
borealis in their puberulent rhachises and subaxillary spines, but are to 
a certain extent intermediate between JM. depauperata on the one hand 
and M. acanthocarpa and M. biuncifera on the other. Without better 
and more copious material their affinities and proper status cannot be 
more exactly determined. : 
t— 650. M. Pringlei, Wars. Branching shrub armed with mostly 
geminate infra-stipular spines: pinne 1 to 2 pairs; leaflets 2 to 4 pairs, 
elliptical or oval, pale green: flowers canescent-puberulent; bracts 
inconspicuous: pods glabrous, 2 cm. long, acute, slightly armed on one 
edge or unarmed. — Proc. Am. Acad. xxi. 452. — Near Big Caiion of 
the Rio Grande, W. Texas, Havard, no. 12, and on rocky hills near 
town of Chihuahua, Pringle, in fruit, October, no. 545, and in flower, — 
August, no. 724. 
© © Pinne (at least on well developed leaves) 8 to oc pairs; leaflets mostly numerous. 
+ Pods 7 to 10 mm. broad, mostly obtuse or obtusish. 
- 52. M. Grahami, Gray. Stem nearly glabrous: primary rha- 
chises (nearly 1 dm. in length) sparingly pubescent; pinne about 10 
pairs; leaflets 15 to 20 pairs narrowly oblong, of firm texture, paler and 
prominently veined beneath, entirely glabrous upon both surfaces, usually 
devoid even of ciliation: pods glabrous at maturity. — Pl. Wright. 1. 
52. — Mountain valleys of Northern Sonora, near the Arizonan bound- 
ary, Wright, no. 1042 
58. M. Lemmoni, Gray. Apparently an undershrub, covered 
with soft and canescent pubescence or tomentum: pinnae about 6 pairs; 
primary rhachis 6 to 10 cm. long; secondary rhachises often 4 — 
in length; leaflets elliptic-oblong, pubescent-tomentose, 5 to 7 mm. 1m 
length: heads numerous, globular, borne on filiform geminate peduncles 
which are sometimes grouped in showy compound racemes: pods even 
at maturity canescent-tomentose. — Proc. Am. Acad. xix. 76. — Hua- 
chuca Mountains, Arizona, Lemmon, nos. 2692, 2693, Pringle, no. 7s 
Toumey, no. 389. Too near the next, from which it differs chiefly in 1 
smaller spines, less woody stems, and larger less crowded leaflets. — 
te 54. M. acanthocarpa, Bent. Stems and branches decidedly 
- ligneous: spines mostly numerous, slender or stout, usually paired and 
infra-stipular, with or without a third one beneath the leaf-insertions 
_ Scattered spines sometimes present also: leaves (except on young and 
