SUNFLOWER FAMILY. 501 



young, the wool more or less deciduous in age; peduncles 3 to 8 in. 

 or even 2 ft. high; leaves not rarely as long as the peduncles, pin- 

 nately parted into narrowly linear or lanceolate retrorse segments, the 

 rachis linear and the lohes more or less remote; outer hracts of involu- 

 cre broad; inner linear and narrowly acuminate, as long as the 

 pappus; ligules short; achenes 2?. to 3 lines long, passing abruptly 

 into the slender (9 or 10 lines long) beak. — (Troximon retrorsum 

 Gray.) 



Mountain summits from Mendocino Co. southward to ilt. Diablo 

 and the ranges at the head of the San Joaquin Valley. !May-June. 



15. LACTUCA Toum. Lettuce. 



Tall leafy-stemmed annuals or biennials with panicled heads of 

 yellow flowers. Leaves alternate. Involucre cylindrical or in fruit 

 conical, its bracts imbricated in 2 or more series of unequal lengths. 

 Kays 5-toothed at summit. Achenes obcompressed, i. e., flattened 

 parallel to the bracts, ribbed on each side, abruptly contracted into a 

 beak, which bears at its dilated summit a copious very soft and white 

 capillary pappus, the hairs of which fall separately. (Ancient Latin, 

 from lac, milk, referring to the milky juice.) 



1. L. Scariola L. Prickly Lettuce. Stem paniculately 

 branched above, glabrous throughout, or hirsute or prickly below, 

 2 to o ft. high; leaves oblong or oblong-lanceolate, denticulate or 

 pinnatifid, sessile or sagittate-clasping, with a row of soft prickles on 

 the midrib; heads numerous in an open panicle, 9 to 14-flowered; 

 involucre cylindrical, its outer bracts about J the length of the inner; 

 rays cream-yellow; achenes narrowly ohovate, about as long as the 

 filiform beak; pappus white. 



Roadsides and waste places in the Bay Kegion: common grain-field 

 weed of the upper Sacramento Valley. June-July. 



L. SATIVA L., Common Lettuce, may be distinguished by the un- 

 armed midrib of the thin foliage. — An escape by roadsides at Santa 

 Clara, Drn-y. and in Xapa Valley fields, ace. to Greene. 



16. SONCHUS L. Sow-thistle. 

 Leafy-stemmed coarse annual weeds, chiefly smooth and glaucous. 

 Heads corymbed or umbellate, swollen at base, or jug-shaped. In- 

 volucral hracts few, thin, with many shorter ones at base; these be- 

 coming callous-thickened. Achenes obcompressed, ribbed, not 

 beaked. Pappus copious, of cottony-white exceedingly soft and fine 

 hairs, mainly falling together. (Greek name of the Sow-thistle.) 



Leaves when sessile usually sagittate-clasping ; peduncles smootli ; achenes 

 longitudinally ribbed and transversely rugose 1. S. oleraceus. 



Leaves when sessile usually auriculate-clasping; peduncles liispid with 

 short spreading gland-tipped hairs; achenes with 3 ribs on each side, 

 the intervals smooth . . . .... . 2. S. asper. 



1. S. oleraceus L. Common Sow-thistle. Stem erect, nearly 

 simple, 1 to 3 or 4 ft. high; leaves lyrately or runcinately pinnatifid, 

 the terminal segment commonly large and triangular, denticulate or 



