PLANT : Glabrous subshrubs or suffrutescent herbs, 1.0-2.5 m tall. STEMS : purple-red, repeatedly branching into slender wand-like capillary branchlets, sparsely glandular, with few fine, long hairs. LEAVES : 0.5-2.5 cm long, short-petiolate; leaflets oblong-obovate, 3-5 mm long, 1-2 mm wide, gland dotted especially around the margins, glabrous. INFLORESCENCE : an open finely branched panicle, the branches 2-6 cm long. FLOWERS : 4-6 mm long; calyx lobes ovate, ca. 0.8 mm long, obtuse, shorter than the tube, unribbed and without prominent veins, glabrous; petals dark rose-purple and whitish. FRUIT : a plumply obovoid pod, 2.7-2.9 mm long, glandular distally. NOTES : Brushy hillsides: Santa Cruz Co. (Fig. 1C); 1350-1500 m (4500-5000 ft); Sep-Oct. Mex., Guatemala. The Mexican name for this plant is Escoba Colorada (Red Broom) in reference to the reddish stems. The species is recognized by Barneby (1977) to have two varieties. The only AZ collection (Hodgson et al. 4771, ASU, DES) appears to be M. diffusa var. diffusa. The leaves are early deciduous and during the dry season individuals look like a clump of red-purple branches terminating in masses of slender panicles. REFERENCES : Rhodes, Suzanne, June Beasley and Tina Ayers. 2011. Fabaceae. CANOTIA 7: 1-13.