coarsely toothed; heads clustered at the summit of stem or rarely solitary, usually 

 overtopped by the subtending leaves or the inflorescence sometimes elongate but 

 still dense; involucre 2-3.5 cm. high, usually glabrous or nearly so; phyllaries 

 rather broad, well-imbricate, the outer with a short mostly erect spine tip, the 

 inner innocuous and often with a dilated scarious fringed tip; corollas whitish to 

 pale-pink or purplish, unequally cleft, the deepest sinuses mostly 5-8 mm. deep, 

 the tube mostly 1 or 2 times as long as the throat. C. Drummondii T. & G., C. 

 acaulescens (Gray) Daniels. 



In wet meadows, low woods along streams and seepage areas, in N. M. (Rio 

 Arriba and Taos cos.) and Ariz. (Apache, Coconino and Greenlee cos.), July- 

 Sept.; Sask. to B.C., s. to N.M., Ariz, and Calif. 



49. Lactuca L. Lettuce 



Mostly biennial or winter annual herbs; leaves alternate, lobed or not, mar- 

 ginally serrate and often with each tooth slightly spinose, the upper ones (at 

 least) often clasping: stems tall, erect, mostly simple except in the upper (head- 

 bearing) region; involucre narrowly urceolate just before anthesis, usually after 

 anthesis becoming more or less campanulate; phyllaries well-imbricated, mostly erect 

 (tips sometimes spreading), ovate-lanceolate to lanceolate or lance-linear, green 

 with narrow white margin; receptacle flattish, naked; flowers 5 to 35 per head, 

 perfect, fertile; corollas yellow, blue, white, rosy-white or lavender, bilaterally 

 symmetrical, the raylike portion terminally 5-toothed; achenes definitely flattened, 

 some extremely flat and even slightly winged, with a definite body portion below 

 which is usually obovate or elliptic in outline and abruptly narrowed to a long 

 or short thick or thin (or even filiform) beak, the microscopic apex flared as a 

 pappus pedestal; pappus of numerous white or whitish capillary bristles, persistent 

 or tardily deciduous as individual bristles (not as a unit). 



An Old World genus of perhaps 100 species. Lactuca sativa L., the cultivated 

 lettuce, a native of Europe, is probably the best-known species of the genus, 

 but most of our species are native. Some of our species hybridize, thus making 

 determinations troublesome. The young leaves of all species are used for salads 

 and greens. 



1. Achenial beak absent or stout, only 0.5-1 mm. long (2) 



1. Achenial beak filiform, 2-4 mm. long (3) 



2(1). Rhizomatous perennial; involucre at anthesis 12-15 mm. high 



4. L. pulchella. 



2. Annual; involucre at anthesis 9-10 mm. high 5. L. floridana. 



3(1). Achene about a third as thick as broad, on each face with about 7 distinct 

 longitudinal nerves, the short wings of the upper sides being pubes- 

 cent 1. L. Serriola. 



3. Achenes very flat, each face with 1, 2 or 3 longitudinal nerves the wings (if 



present) not pubescent (4) 



4(3). Lower leaves mostly linear, 10-33 cm. long, 5-12 mm. broad 



3. L. graininifolia. 



4. Lower leaves not linear or (if so) proportionately broader 2. L. canadensis. 



1. Lactuca Serriola L. Prickly lettuce. Fig. 782. 



Taprooted annual or winter annual; stems (3-) 5-20 dm. tall, erect, simple 

 except in the uppermost reaches; leaves usually pinnatifid (except the uppermost) 

 and usually clasping, the margins usually finely spinose-dentate; involucres 8-1 1 

 mm. long at anthesis, 9-13 mm. long in fruit, the inner (longer) phyllaries after 

 anthesis becoming filiform-involute for most of their length; corollas yellow 

 (often the extreme tip discolored bluish or purplish); achene body 2.5-3 mm. long, 



1698 



