180 BOTANY. 



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

 margins; heads many, 1-1 J' in diameter, the Bubtending 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 dilate; 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. — Chirk-alma, 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 poly cephalous ; 

 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 membranace< >us 

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

 description. — Arizona. 



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

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

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

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



* Centadrba, L. — Head* many-flowered ; ray-flowers mostly large and sterile, some times wanting; 

 involucre various, imbricated. Rcceptaclo setose. Acbenia compressed. Pappus occasionally wanting 

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

 smaller and somewhat eonnivent. — T. & G. 



tl'KKK/.i.v. Lagasea. — " Head several-many-ilowered ; the flowers all perfect. Involucre turbinate 

 or campannlate; its scales imbricated, lanceolate or oblong, moBtly cbartaceons. Receptacle flat and 

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

 inner '2-toolhed or 'J-clclt. Anthers with long nuked tails at base, and a lanceolate terminal appendage. 



Akenes elongated-oblong, terete or slightly aDgled, often obscurely narrowed at apex, commonly glandu- 

 lar. Pappus of copious scabrous capillary bristles.— Herbs; with alternate and mostly rigid 1< tares, and 



solitary or usually paniculate heads of purple or white (lowers."— Okay, I'l. Cal. 1. p. 129 



