Spring Flora of Oklahoma 
203 
4. Gaillardia trinervate Small. Rayless Gaillardia. Similar 
to G. suavis in habit. Leaves spatulate or oblong-spatulate, merely 
toothed, 3-ribbed. Scape closely pubescent under the head. Involu- 
cral bracts reflexed. Rays none. 
In dry soil. April-June. Frequent. 
XXV. ACHILLEA (Vaill.) L. 
Perennial. Leaves alternate, pinnately divided. Heads 
with ray flowers in a terminal corymb. Involucral bracts 
imbricated in several series, the outer shorter. Receptacle 
chaffy. Ray-flowers white or pink, pistillate and fertile. 
Disk-flowers bi-sexual, tubular, 5-lobed. Achenes oblong, 
compressed, slightly margined. Pappus none. 
Plant loosely woolly or nearly glabrous; inflorescence 
flat-topped. 1. A. Millefolium . 
Plant densely woolly; inflorescence convex. 2. A. lanulosa. 
1. Achillea Millefolium L. Yarrow. Perennial. Flowering 
stems pubescent or nearly glabrous, 12'-24' high. Basal leaves mostly 
petioled, sometimes 10' long, and finely dissected into narrow, pin¬ 
na tifid segments, tomentose, pubescent or neary glabrous. Heads nu¬ 
merous, 2"-3" broad, in terminal compound corymbs. Rays 4-6, 
white, or often pink or purple, less than 2" broad. 
On prairies. May-November. Common. 
2. Achillea lanulosa Nutt. Woolly Yarrow. Similar to the 
preceding species, l°-2%° high, densely silky-woolly nearly all over. 
Leaves deeply bi-pinnatifid into narrow lobes and segments. Inflo- 
resence convex, 2'-4' broad. Involucral bracts greenish-yellow, with 
brownish margins. Rays l"-2t£" broad, white. 
In dry soil. May-September. Common. 
XXVI. SENECIO (Tourn.) L. 
Annual or perennial herbs. Leaves alternate or basal. 
Heads many flowered, solitary, corymbose or paniculate, 
yellow. Involucre cylindric or campanulate, bracts in 1 
series, distinct, or united at the base, usually with some 
shorter, outer ones. Receptacle flat, naked. Rays, when 
present, pistillate, fertile. Disk-flowers perfect, fertile, 5- 
toothed or 5-lobed. Achenes terete or compressed, 5-10- 
ribbed, papillose or canescent. Pappus of numerous, slen¬ 
der or capillary, smooth or rough, mostly white bristles. 
