542 COMPOSITAE (COMPOSITE FAMILY) 



more or less bur-like, being armed over the surface with several or numerous 

 prickles or spines (the spiny free tips of the component bracts) in more than 1 

 series. Leaves mostly alternate. 



Leaves twice or thrice pinnately dissected. 



Annuals 1. F. acanthicarpa. 



Perennials. 



Leaves regularly pinnate, the lobes linear or narrowly oblong . 2. F. tenuifolia. 



Leaves interruptedly pinnate, the lobes ovate or triangular . . 3. F. tomentosa. 



Leaves simple or simply pinnate . . . . . . . 4. F. Grayi. 



1. Franseria acanthicarpa (Hook.) Coville, Contr. U. S. Nat. Herb. 4: 129. 

 1903. Diffusely spreading or sometimes rather strict, 3-6 dm. or more high, 

 from an annual or more enduring (?) root; in age scabrous or short-hirsute and 

 somewhat canescent: leaves on long petioles, broadly ovate in outline, once 

 or twice pinnatifid into short, rounded, often toothed lobes: staminate racemes 

 solitary or in small panicles, the heads nodding on short slender peduncles; 

 fruiting involucres in the axils below, either solitary or 2 or 3 together, 1- 

 flowered, glabrous; spines flat, thin, lanceolate-subulate, with straight or 

 slightly curved but not uncinate tips. F. Hookeriana. Common on sandy 

 plains; throughout our range and westward to the coast. 



2. Franseria tenuifolia Gray, PI. Fendl. 80. 1848. Erect, 3-10 dm. high, 

 leafy to the top, hispid, variously pubescent, or glabrate: leaves mostly 2-3- 

 pinnately parted or dissected into narrowly oblong or linear lobes, the ter- 

 minal elongated: sterile racemes commonly elongated and paniculate; fertile 

 heads in numerous glomerules below, in fruit minutely glandular, usually 

 2-flowered, armed with 6-18 short and stout incurving spines, their tips 

 almost always hooked, and an excavated cartilaginously bordered areola 

 above each. (Gaertneria linearis Rydb. Bull. Torr. Bot. Club 32: 133. 1905.) 

 Kansas and Colorado to Texas and California. 



3. Franseria tomentosa (Nutt.) A. Nels. Erect from perennial slender 

 creeping rootstocks, 1-3 dm. high: leaves canescently tomentose beneath, 

 green and glabrate above, interruptedly pinnatifid, oblong in outline, com- 

 paratively large, the lowest often 8-12 cm. long; the lobes usually short and 

 broad: sterile racemes commonly solitary; fruiting involucre 2-flowered, 

 canescent, armed with rather short, conical-subulate, very acute, and straight 

 spines. (Ambrosia tomentosa Nutt.; F. discolor Nutt.; Gaertneria tomentosa 

 A. Nels. Bot. Gaz. 34: 34. 1902.) A most ineradicable weed in cultivated 

 ground; Montana to New Mexico. 



4. Franseria Grayi A. Nels. Stems about 3 dm. high, rather stout, erect, 

 from an apparently perennial base, canescent with a dense sericeous tomen- 

 tum: leaves very white beneath, cinereous above, pinnately 3-5-cleft or 

 parted; the terminal division large, oblong or broadly lanceolate, serrate; 

 upper lateral similar but smaller; the lowest commonly very small and entire: 

 fruiting involucre 6 mm. long, 2-flowered, nearly glabrous; the short spines 

 conical-subulate, very acute, and the very tip usually uncinate-incurved. 

 (F. tomentosa Gray, PI. Fendl. 80. 1848; Gaertneria Grayi A. Nels. 1. c. 35.) 

 Along streams; Kansas, Nebraska, and eastern Colorado. 



44. XANTHIUM L. COCKLEBUR 



Coarse annual weeds with widely branching and very stout stems. Leaves 

 alternate, toothed or lobed, petioled. Heads unisexual, the flowers greenish. 

 Staminate heads subglobose, in a terminal cluster; involucre of several dis- 

 tinct narrow bracts in 1 or 2 series; receptacle cylindrical; flowers mimy, 

 separated by the bracts of the receptacle; corolla tubular. Pistillate heads 

 axillary, below the staminate; involucre closed, forming in fruit an ovoid or 

 oblong indurated bur covered with hooked prickles, 1 or 2-beaked, 2-celled, 

 each cell containing 1 seed; corolla none; pappus none; style 2-cleft, the 

 branches exserted through the beaks. 



1. Xanthium echinatum Murr. Comm. Goett. 6: 32. 1783. Stem often 

 punctate with brown spots: leaves cordate or ovate, 3-ribbed from the base, 



