STANDLEY TUBES AND SHRUBS OF MEXICO 1513 



Heavy-scented shrub about 1 meter high, much branched, thinly gray-tomen- 

 tose, glabrescent; leaves alternate, 5 to IS mm. long, 3-toothed or 3-cleft, with 

 linear lobes, fleshy; heads 8 to 10 mm. high, in small terminal cymose panicles, 

 about 21-flowered; involucre 2-seriate, subequal, 4 to 5 mm. high, the phyllaries 

 lanceolate, obtuse, appressed, subherbaceous, tomentulose; flowers all hermaphro- 

 dite, tubular; anthers sagittate-caudate; achenes oblong-turbinate, densely 

 silky-pubescent, 2 mm. long; pappus 4 mm. long, stiff, of about 10 longer barbel- 

 late bristles and about three times as many irregularly somewhat connate shorter 

 bristles. 



35. NOCCA Cav. Icon. PI. 3: 12. pi. 224. 1795. 

 Reference: Robinson, Synopsis of the genus Nocca, Proc. Amer. Acad. 36: 

 467-471. 1901. 



Shrubs or herbs; leaves mostly opposite; heads 1 or 2-flowered, densely 

 crowded at tips of stem and branches in campanulate or globose glomerules, 

 these subtended by herbaceous bracts; proper involucre tubular, gamophyllous, 

 5 or 6-toothed; corollas tubular, yellow, white, or purple, exserted; achene 

 columnar; pappus a short cup, usually with awns or squamellae added. 



Involucres 2-flowered 1. N. biflora. 



Involucres 1-flowered. 



Leaves sessile, cordate-clasping. 



Inflorescence short, leafy-bracted; leaves all with broadly clasping base. 



2. N. helianthifolia. 

 Inflorescence elongate, the bracts small; lower leaves sessile, not clasping. 



3. N. media. 

 Leaves petiola.te (the petiole rarely leafy-margined), not cordate-clasping. 

 Glomerules campanulate, sessile or subsessile. 



Leaves densely silvery-silky beneath at maturity. 



4. N. heteropappus. 

 Xeaves not densely silvery-silky beneath at maturity, sometimes slightly 

 so when young in no. 7. 

 Leaves finely serrulate with purple-glandular teeth (about 10 per cm.). 



5. N. mocinniana. 

 Leaves coarsely serrate (teeth 2 to 4 per cm.) to subentire. 



Stem finely puberulous with appressed hairs, also more or less glandu- 

 lar, without long spreading hairs 6. N. rigida. 



Stem pubescent with long wide-spreading hairs, at least in the in- 

 florescence, as well as glandular. 

 Leaves elliptic to lance-oblong, three to five times as long as wide. 



7. N. angustifolia. 

 Leaves ovate or lance-ovate, two and one-half times as long as 

 wide, or less. 

 Leaves green beneath; petioles usually winged. 



8. N. pteropoda. 

 Leaves griseous-pubescent beneath; petioles naked. 



Leaves broadly ovate, 5.5 to 7 cm. long; branches of inflores- 

 cence elongate, divergent 9. N. pringlei. 



Leaves lance-ovate, 7.5 to 12.5 cm. long; inflorescence con- 

 tracted, its branches suppressed 10. N. tomentosa. 



Glomerules globose or subglobose, slender-peduncled. 

 Teeth of the proper involucres lance-subulate. 



Leaves subsericeous-pilose beneath with appressed hairs; proper in- 

 volucres silky-villous 11. N. decipiens. 



Leaves rather harshly pubescent beneath; proper involucres usually 

 hirsute 12. N. glandulosa. 



