274 University of California Publications in Botany. [VOL. 3 



degee reports it as abundant and appearing as though native on 

 the Todos Santos, Natividad, Cedros, San Martin, and Guadalupe 

 islands, all off the coast of Lower California, and at San Jorge, 

 on the mainland. 



117. LACTUCA Tourn. LETTUCE. 



Tall leafy-stemmed herbs with panicled heads of (in our 

 species) yellow flowers. Leaves alternate. Involucre cylindrical 

 or in fruit conical, its bracts imbricated in 2 or more series of 

 unequal lengths. Rays 5-toothed at summit. Achenes obcom- 

 pressed, i.e., flattened parallel to the bracts, 1 to 5-nerved on each 

 face, contracted into a beak, which bears at its dilated summit a 

 copious very soft and white or brown capillary pappus, the hairs 

 of which fall separately. 



1. L. Scariola var. integrata Gren. & Godr., Fl. France ii. 320 

 (1850) ; Dewey, Rhodora vii. 11 (1905). PRICKLY LETTUCE. 



Plant 6 to 18 dm. high, branching above into an open panicle, 

 glabrous throughout or hirsute or prickly below : leaves oblong 

 or oblong-lanceolate, sessile or sagittate-clasping, with a row of 

 soft prickles on the midrib and along the margins : heads numer- 

 ous, 6 to 14-flowered : involucre 10 to 14 mm. high ; its outer 

 bracts much shorter than the inner : rays cream-yellow changing 

 to blue : achenes light brownish gray, narrowly obovate, about as 

 long as the filiform beak, striate, margined : pappus white. 



An introduced European weed which, during the last decade, 

 has become exceedingly abundant on waste lots and along road- 

 sides near Los Angeles, San Bernardino, etc. Typical L. Scariola 

 L., which has apparently not yet appeared in Southern California, 

 has runcinate or pinnately lobed leaves. 



L. SATIVA L., the common Lettuce, may be found as an escape 

 from gardens. It has broad and tender root-leaves and cordate- 

 clasping stem-leaves. 



L. LUDOVICIANA (Nutt.) DC., of the middle states, may occur 

 as an immigrant. It has black achenes, lightly 1-nerved on each 

 face : involucre 2.5 to 3 cm. high. 



