180 BOTANY. 



the teeth tipped with longer spines than are found on the inter-dental 

 margins; heads many, 1-1 J' in diameter, the subtending bracts spiny- 

 margined and tipped; outer involucral scales strongly ciliate-fringed ; inner 

 ones less so, except at the tip, which has a small, oblong, ciliate, spine-tipped 

 appendage 1-2" long and half as wide ; flowers light yellow. — Twin Lakes, 



Colorado (460). 



Centaurea* Americana, Nutt— Erect, 4°, smooth; leaves sessile, 

 entire, glabrous or nearly so, but with margins slightly ciliate; heads, 

 including the long purple rays, 4' in diameter ; outer scales of the involucre 

 very short and tipped with a lanceolate, brown, pectinate-ciliate appendage 

 as long, or longer than the scales, the inner series becoming regularly longer 

 and more scarious, the appendage remaining same size as in the outer 

 series; pappus of rigid, similar, roughish bristles. — Chiricahua, Southern 

 Arizona (527). 



• PEREZiAf Wrightii, Gray (PI. Wright. 1, p. 127).— " Smoothish; the 

 leafy herbaceous stem 2° high, from a perennial root; leaves thin, mem- 

 branaceous, oblong-ovate, spinulose-denticulate, the larger doubly dentate, 

 sessile and at base often auriculate; compound corymb polycephalous ; 

 heads 8-10-flowered, sub-fasciculate, involucre viscid sub-puberulent, scales 

 hardly in 3 series, oblong and rather obtuse; achenia glandular, the soft 

 white pappus of delicate bristles. Well distinguished by its membranaceous 

 leaves and small heads" Not having the plant, I have quoted the original 

 description. — Arizona. 



Perezia nana, Gray (PI. Fendl. p. 111). — 2"-12' high, the single- 

 headed leafy branches erect from a woolly, creeping root; leaves thickish, 

 strongly reticulate, ovate or a little cuneate at base, sessile, very irregularly 

 toothed, teeth spiny or mucronate-tipped from the produced nerves; heads 



* Centaurea, L. — Heads many -flowered ; ray-flowers mostly large and sterile, sometimes wanting ; 

 involucre various, imbricated. Receptacle setose. Achenia compressed. Pappus occasionally wanting 

 or nearly so, but usually composed of scabrous filiform bristles, in one or more series, the inner often 

 smaller and somewhat counivent. — T. & G. 



tPsREZiA, Lagasca. — "Head several-many-flowered; the flowers all perfect. Involucre turbinate 

 or campanulate; its scales imbricated, lanceolate or oblong, mostly chartaceous. Receptacle flat and 

 naked. Corolla with a slender tube and bilabiate limb; the outer lip much longer and 3-toothed; the 

 inuer 2-toothed or 2-cleft. Anthers with long naked tails at base, and a lanceolate terminal appendage. 

 Akenes elongated-oblong, terete or slightly angled, often obscurely narrowed at apes, commonly glandu- 

 lar. Pappus of copious scabrous capillary bristles.— Herbs ; with alternate and mostly rigid leaves, and 

 solitary or usually paniculate heads of purple or white flowers."— Gray, PI. Cal. 1, p. '122. 



