Lactuca Compositae 1009 



3. Sonchusasper (L.) Hill. Spinyleaf Sow Thistle. Map 2215. This 

 is more common than the preceding species and found in similar habitats. 

 Nat. of Eu. ; now a weed in all cultivated parts of the world. 



9596. LACTUCA [Tourn.] L. Lettuce 



Achenes with filiform beaks, flat, with thin margins. 

 Margins of leaves, and usually their midribs prickly. 

 Achenes light brown, not shining. 



Sides of achenes with 3-6 longitudinal, scabrous ribs, hispid at the summit; beak 

 about as long as the body of the achene; rays yellow. 



Leaves runcinate-pinnatifid, the segments mostly 5 or 7 1. L. Scariola. 



Leaves spinulose-denticulate, not pinnatifid.. . la. L. Scariola var. integrata. 

 Sides of achenes with one rib, otherwise similar to the preceding; rays pinkish 



purple 2. L. campestris. 



Achenes black, shining. (See excluded species no. 702, p. 1105) L. virosa. 



Margins of leaves not prickly but the leaves sometimes with sharp teeth. 



Achenes light brown, body 2.5-3 mm long, their beaks twice as long as their bodies, 



usually with 6-9 longitudinal, scabrous ribs, not hispid at the apex 



3. L. saligna. 



Achenes dark brown with a mottling of black, minutely and closely marked with 

 transverse ridges, with one prominent longitudinal ridge on each face. 

 Involucres 10-14 mm long; mature achenes 5-6 mm long; pappus 5-7 mm long. 

 Leaves all, or at least the lower ones, more or less lobed. 



Leaves with linear-falcate, usually entire lobes; upper unlobed leaves, if 



any, linear or linear-lanceolate; base of leaf sagittate or auriculate 



4. L. canadensis var. typica. 



Leaves with broadly falcate, or obovate and obliquely truncate, entire or 

 toothed lobes; upper leaves similar or unlobed and lanceolate, rarely 

 oblanceolate or obovate, entire or toothed, sagittate, and clasping at 



the base 4a. L. canadensis var. latifolia. 



Leaves all unlobed, lanceolate, oblong, oblanceolate or obovate, entire or 

 denticulate, the lowest sometimes with shallow lobes. 

 Cauline leaves lanceolate to ovate-lanceolate, entire or toothed. 



Base of leaf sagittate, clasping 4b. L. canadensis var. integrifolia. 



Base of leaf tapering, not sagittate 



4c. L. canadensis var. integrifolia f. angustata. 



Cauline leaves oblanceolate or obovate, usually toothed, sagittate, and 



and clasping at the base 4d. L. canadensis var. obovata. 



Involucres 16-22 mm long; mature achenes 7-9 mm, including the beak; pappus 



9-12 mm long. (See excluded species no. 700, p. 1105) L. hirsuta. 



Achenes without filiform beaks, beakless or essentially so; rays bluish, sometimes 

 cream color in Lactuca spicata. 

 Pappus white. 



Leaves coarsely and unevenly dentate, acuminate at the apex, long taper-pointed 

 at the base, sessile, not sagittate, more or less sparingly pubescent above and 

 beneath, the pubescence usually restricted to the principal veins, sometimes 



nearly glabrous, and rarely the pubescence conspicuous 5. L. villosa. 



Leaves lyrately cut into 3-6 segments, the terminal segment usually the largest 

 and triangular with about equal sides, sometimes one or more of the upper 



leaves not lobed, glabrous or nearly so 6. L. floridana. 



Pappus tawny; very large plants with bluish or cream color flowers; latex white or 

 tawny. 



