FLOE A OF THE DISTRICT OF COLUMBIA. 265 



4. LEONTODON L 



Achenes greenish brown; heads 3-5 cm. broad; bracts green, the outer ones reflexed, 

 without cylindric appendages at the tips; pappus white 1. L. taraxacum. 



Achenes red or reddish brown; heads 2-3 cm. broad; bracts erect or ascending, with 

 cylindric appendages at the tips; pappus dirty white 2. L. erythrospermum. 



1. Leontodon taraxacum L. Common dandelion. 

 Waste ground, open fields, and lawns; very abundant. Apr.-June. Native of Eur. 



and Asia; naturalized nearly throughout N. Amer.; perhaps native in the western 

 U. S. ( Taraxacum officinale Weber; T. taraxacum Karat. ; T. dens-leonis Deef.) 



The plants may be found in flower at nearly any time of the year, even in midwinter 

 if there are a few warm days. The leaves are much used for "greens. " Plants with 

 branched scapes occur occasionally; in one collected in the Department of Agriculture 

 grounds in 1893, the outermost bracts have assumed the form of leaves 1-2.5 cm. long. 



2. Leontodon erythrospermum (Andrzej.)Britton. Bed-seeded dandelion. 

 Waste ground; frequent. Apr.-Aug. Native of Eur.; widely naturalized in N. 



Amer. (Taraxacum erythrospermum Andrzej.) 



5. CHONDRILLA L. 



1. Chondrilla juncea L. Skeleton-weed 



Waste and cultivated ground; common. May-Oct. Native of Eur.; naturalized 



from Del. to Va. 



This plant is often very abundant in Maryland and Virginia, but in spite of the 

 adaptation of its seeds to dispersal by wind and other means, it has not spread to other 

 parts of the United States. 



6. PRENANTHES L. 



Pappus deep reddish brown; involucre glabrous, cylindric 1. P. alba . 



Pappus pale brown; involucre usually bearing a few long hairs, the bracts abruptly 

 spreading above the middle 2. P. serpentaria. 



1. Prenanthes alba L. Rattlesnake-root. 

 Moist or dry woods; common. Sept.-Oct. Eastern U. S. (Nabalus alius Hook.) 

 The lower leaves vary from ovate and ehallowly toothed to hastate or deeply lobed. 



2. Prenanthes serpentaria Pursh. Lion's-foot. 

 Dry or moist woods and fields; common. Aug.-Oct. ■ Eastern U. S. (Nabalus 



serpentarius Hook.; N. fraseri DC.) 



The leaves vary as in the preceding species. A form with merely dentate lower 

 leaves, described as Nabalus integrifolius Cass., is of frequent occurrence. 



7. SONCHTTS L. Sow thistle. 



Achenes ribbed and transversely wrinkled; auricles at the base of the stem leaves 



, 1. S. oleraceus. 



acute 



Achenes ribbed but not transversely wrinkled; auricles of the stem leaves rounded. 



2. S. asper. 



1. Sonchus oleraceus L. 



Waste ground; frequent. June-Oct. Native of Eur.; naturalized in nearly all 

 cultivated parts of the earth. 



2. Sonchus asper (L.) Hill. 



Waste ground; frequent. June-Sept. Native of Eur.; naturalized throughout 

 most cultivated parts of the earth. 



