410 CICHORIACEAE. 



1. Taraxacum Taraxacum (L.) Karst. (T. officinale Weber.) Around 

 dwellings, in fields and on roadsides from Lab. and Wash, to S. C. and Calif. ; 

 naturalized from Europe. Alt. 4000-7000 ft. Minturn, Eagle Co.; La Veta; 

 Ft. Collins. 



2. Taraxacum mexicanum DC. In mountain valleys from Colo, to Mex. 

 Alt. 7000-9000 ft. Pass Creek; Ouray; headwaters of Sangre de Cristo 

 Creek; hills southeast of La Veta; along Uncompahgre River, near Ouray. 



3. Taraxacum dumetorum Greene. (T. oblanceolatum A. Nels.) In moun- 

 tain valleys from Ass. to Colo. Alt. 7000-10,000 ft. Columbine; mountain 

 near Veta Pass; Cucharas River, below La Veta; Mancos; Seven Lakes; Ft. 

 Collins ; Halfway House, Pike's Peak. 



4. Taraxacum leiospermum Rydberg. In the mountains of Colo. Alt. 

 about 10,000 ft. Tennessee Pass ; Seven Lakes ; Cripple Creek. 



5. Taraxacum montanum Nutt. (T. officinale alpinum A. Gray, in part) 

 In the mountains from Mont, to Colo. Alt. about 9500 ft. Chambers' Lake; 

 source of Leroux; Camp Creek. 



6. Taraxacum scopulorum (A. Gray) Rydb. (T. oMcinale scopulorum A. 

 Gray) On the higher peaks in damp places from B. C. to Utah, Colo, and 

 Mont. Alt. 10,000-13,000 ft. West Spanish Peak; Mt. Hesperus. 



15. LACTUCA L. LETTUCE. 



Achenes with a slender beak ; pappus white. 



Outer bracts (calyculum) not more than half as long as the bracts proper ; 



flowers yellow, rarely tinged with blue. 

 Heads 6-8-flowered ; achenes several-nerved, not rugose ; leaves spinulose 



on the ribs. i. L. virosa. 



Heads i2-2o-flowered ; achenes i-3-nerved, transversely rugose. 



Involucres about i cm. high. 2. L. canadensis. 



Involucres 1.5-2 cm. high. 



Leaves obovate or oblanceolate in outline with broad lobes, often spinu- 

 lose on the mid-ribs beneath. 3. L. ludoviciana. 

 Leaves linear or linear-lanceolate in outline, entire or with narrow lobes, 

 never spinulose. 4. L. gramini folia. 

 Outer bracts gradually increasing inwards ; a distinct calyculum therefore not 



evident ; flowers blue. 5. L. pulchella. 



Achenes beakless ; pappus tawny or brown. 6. L. spicata. 



1. Lactuca virosa L. In waste places and fields from Me. and N. D. to 

 Ga. and Calif. ; introduced from Europe. Alt. 5000 ft. Ft. Collins ; Poudre 

 flats. 



2. Lactuca canadensis L. In moist open places from N. S. and Sask. to 

 Fla. and Colo. Alt. 4000-6500 ft. La Porte, Larimer Co.; Hotchkiss; gulch 

 west of Soldier Canon. 



3. Lactuca ludoviciana DC. River banks and moist places from Minn, and 

 Mont, to Mo. and Tex. Alt. 4000-8000 ft. New Windsor; between Sun- 

 shine and Ward; Denver. 



4. Lactuca graminifolia Michx. In rich soil from N. C. and Colo, to Fla. 

 and Ariz. Alt. up to 7500 ft. Along the Uncompahgre River, near Ouray. 



5. Lactuca pulchella DC. In wet meadows from Sask. and Wash, to Mo., 

 N. M. and Calif. Alt. 4000-8000 ft. Cucharas Valley, near La Veta; Ft. 

 Collins; Durango; Clear Creek; Gunnison; Parlin, Gunnison Co.; McCoy; 

 Walsenburg; Montrose; Boulder; Gypsum; Table Rock; Fortification, Routt 

 Co. 



