COMPOSITAE THISTLE FAMILY LETTUCE 761 



i 



to oblong in outline with spinulose, denticular margins occasionally sinuate 

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

 j 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, 

 J 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 canadensls 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; 

 leads 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 

 land 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 

 ijnot liked by cattle although sometimes eaten by sheep. It has been regarded 



