97 
* Pods more or less prickly (rarely unarmed in No, 4), 
+ Pinna 1 or 2 pairs, 
1. M. borealis Gray. Erect and smooth shrub, the branches armed with very stout 
and slightly hooked and scattered infrastipular spines: leaflets 4 or 5 pairs, oval and 
scarcely inequilateral, thickish and glabrous, about 2 mm. long: pod oblong, stipi- 
tate, 2 to 4-seeded and breaking up into as Inany joints, glabrous, the margin sparsely 
spiny.—Said to be a common bush on the Peeos and westward. On dry gravelly 
soil. Var. TEXANA Gray is a form with 5 or 6 pairs of oblong leaflets, 
~ + Pinne 4 to7 pairs, 
2. M. flexuosa Benth, A much branched minutely pruinose-puberulent shrub, 
‘the white rigid flexuous branches armed with conical straight usually paired infra- 
stipular spines: pinne 5 to7 pairs; leaflets 7 to 10 pairs, oblong, obtuse, thickish, 
puberulent, very small, 1 mm, long: pod linear, straight or slightly falcate, minutely 
whitish puberulent, little more than 2.5 em, long, scarcely 4 mm, broad, the mar- 
ginal spines irregular and straight.—Mountain valleys west of the Pecos, 
3. M. Lindheimeri Gray. A smooth or minutely puberulent shrub, the branches 
armed with very stout compressed infrastipular spines (solitary, in pairs, or in 
threes): pinuwe 4 to 6 pairs; leaflets 8 to 12 pairs, oblong ; stipules spinescent : pod 
linear-oblong or falcate, glabrous, the margin sparsely armed with stout somewhat 
hooked spines, ~-Apparently throughout southern and western Texas. Forms oecur 
with the pinne reduced to 2 or 3, 
4. M. biuncifera Benth. A shrub with divaricate pubescent branches and hooked 
usually paired infrastipular spines: pinnie 4 to 6 pairs; leaflets 10 to 15 Pairs, small 
and oblong, glabrous above, pubescent beneath: pod narrowly linear, falcate-incurved 
or sickle shaped, glabrous or nearly so, 2.5 to 3.5 em. long, less than 4 mm. wide, 
the margin more or legs beset with hooked prickles or sometimes naked.—In western 
Texas, most. common on dry gravelly soil west of the Pecos, Dr. Havard reports 
that this species and M. borealis, noted for the abundance and stoutness of their 
prickles, are known ag «« una de gato.” 
** Pods unarmed (rarely armed in Nos. 5 and 7), 
+ Pinne 1 to 3 pairs, 
o. M. fragrans Gray. An erect very smooth shrub, with solitary short and stout 
somewhat recurved infrastipular spines: leaflets 5 or 6 pairs, linear-oblong, 4 mm. 
long or shorter: pod linear, falcate, very smooth, with 6 to 8 thin-chartaceous joints, 
usually much constricted between the seeds.—From the Colorado near Austin south- 
westward to the Rio Grande and westward to New Mexico. Not at all abundant, 
+ + Pinne 4 to 10 pairs. 
++ Leaflets 5 to 14 pairs. 
6. M. malacophylla Gray. A suffrutescent plant, canescent with a fine and very 
soft down, with procumbent stems beset (as well as the petioles) with numerous 
short hooked prickles: pinnew 4 to 7 pairs; leaflets 5 to 8 pairs, ovate or oval-oblong, 
mucronate and veiny, 6 to 10 mm, long: pod broadly linear, acute, rather long stipi- 
tate, very smooth and shining, 6 to 8-seeded, 5 cm. or more long.—In the region of 
the lower Rio Grande. 
7. M. dysocarpa Benth. A shrub with reddish-villous branches and petioles, 
and sparse strong spines: pinnze 6 to 10 pairs; leaflets 8 to 10 pairs, crowded, oblong, 
acute, sericeous-villous, scarcely 4 mm, long: pod linear-faleate, rigidly almost pun- 
gently acuminate, densely clothed with a reddish tomentum, 3.5 to 5 em. long, 6 
mm. broad, occasionally sparsely armed, at length breaking up into joints.—A 
species of western Texas, west of the Pecos, and extending itito contiguous Mexieo 
and New Mexico and Arizona, 
8. M. strigillosa Torr. & Gray, Herbaceous, the stems diffuse and extensively 
procumbent, usually unarmed (occasionally With a very few short prickles), the young 
23204—vol. 2, No. 1—__7 
