SUNFLOWER FAMILY. 419 



imbricated in 2 or more series of unequal lengths. Rays 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 5 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 % the length of 

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

 filiform beak; pappus white. 



Introduced from Europe: roadsides and waste places in the Bay region; 

 common grain-field weed of the upper Sacramento Valley, where its hemp- 

 like fibres sometimes choke and destroy the separating machines of combined 

 harvesters. L. sativa L., with unarmed midrib, is the common Lettuce of the 

 gardens. June-July. 



TARAXACUM Ludwig. Perennial or biennial herbs with radical pinnatifid 

 or runcinate leaves and large yellow-flowered heads solitary on a slender hollow 

 scape. Involucre double, the outer bracts spreading or reflexed, the inner 

 bracts erect in a single row. Achenes 4 or 5-ribbed, prolonged at apex into a 

 very slender beak, bearing the copious soft white capillary pappus. T. 

 officinale Weber. Common Dandelion. Frequent in lawns; locally established 

 in Xapa Valley, etc. 



16. SONCHUS L. Sow-Thistle. 



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

 corymbed or umbellate, swollen at base, or jug-shaped. Involucral bracts few, 

 thin, with many shorter ones at base; these becoming callous-thickened. 

 Achenes obcompressed, ribbed, not beaked. Pappus copious, of cottony-white 

 exceedinglv soft and fine hairs, mainly falling together. (Greek name of the 

 Sow-thistle.) 



Leaves when sessile usually sagittate-clasping; peduncles smooth; achenes longitudinally 

 ribbed and transversely rugose 1. 5". oleraceus. 



Leaves when sessile usually auriculate-clasping; peduncles hispid with short spreading gland- 

 tipped hairs; achenes with 3 ribs on each side, the intervals smooth 2. 5". 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 toothed, sagittately clasping at 

 base, with acute lobes; lower leaves petioled; uppermost sessile and commonly 

 lanceolate; heads about % in. broad when expanded; achenes longitudinally 

 ribbed and transversely rugose. 



Naturalized European weed: old fields and waste places, flowering at all 

 seasons. 



2. S. asper L. PBICKLY Sow-Thistle. Very similar to the preceding, but 

 the Leaves sometimes undivided and commonly clasping by an auricled base, the 

 auricles rounded; achenes flat, margined with a narrow wing and marked on 

 each side with 3 longitudinal ribs; intervals between the ribs smooth, but the 

 ribs as well as the marginal wing rugulose or serrulate; peduncles conspicuously 

 hirsute with spreading gland-tipped hairs. 



Naturalized European weed: with the preceding but apparently not so com- 

 mon. There are hybrid-like intermediates. 



