COMPOSITAE THISTLE FAMILY LETTUCE 761 



to oblong in outline with spinulose, denticular margins occasionally sinuate 

 toothed, sometimes pinnatifid; base sagittate clasping; leaves becoming vertical 

 by a twist; the leaves are not twisted in shady situations; flowers in small open 

 panicled heads; each head has from 4-18 yellow flowers; achenes flat, striate 

 nerved, obovate, oblong, produced in long filiform beak which is paler in color 

 th?n the achene; pappus consists of delicate white bristles arising at the end 

 of the beak. 



Distribution. Prickly lettuce is a native of temperate and southern Europe, 

 Canary Islands, Maderia, Algeria, Abyssinia, and the temperate regions of 

 eastern Asia. It was introduced into North America about 1863. 



Fig. 440. Prickly Lettuce (Lac- 

 tuca Scariola). After Fitch. 



Lactuca canadensis L. Wild Lettuce 



A tall, leafy, smooth or occasionally somewhat hairy biennial 4-9 feet high ; 

 leaves 6-12 inches long; stem leaves sessile or auriculate clasping, the upper 

 leaves smaller, lanceolate acuminate and entire; heads with about 20 flowers in 

 spreading panicles; involucre cylindrical; rays yellow; achene somewhat longer 

 than the beak. 



Distribution. In moist places, borders of thickets and in fields from Nova 

 Scotia to Manitoba, south to Arkansas, Louisiana and Georgia. 



Lactuca pulchella (Pursh.) D. C. Blue Lettuce 

 A glabrous perennial, with milky juice, simple stem from 1-2 feet high, 



sessile, oblong or linear lanceolate entire leaves the lower runcinate-pinnatifid ; 



heads corymbose paniculate, peduncles with scaly bracts; scales of the involucre 



imbricated in 3 or 4 ranks; flowers blue; achenes oblong lanceolate, somewhat 



flattened. 



Distribution. Native to the plains from western Iowa north to Manitoba 



and west to the Great Basin and California, and rare as far east as Michigan. 



A troublesome weed in grain fields of Montana and Utah. 



Poisonous properties. The wild blue lettuce is common in the west but is 



not liked by cattle although sometimes eaten by sheep. It has been regarded 



