192 



GENUS CHRYSOTHAMNUS. 



long bracts to filif alius. This is useful in that it calls attention to the fact that this 

 narrow-leaved, small-headed form has a more compact inflorescence than typicus. 

 However, the individual heads in the latter are also sometimes sessile (for example, 

 Purpvs, 626 J^), while the variation in the length of the subtending bracts does not vary 

 in unison with other characters. Since the two forms occupy the same general terri- 

 tory, careful field observations should be made to see if they are not entirely ecologic 

 in their origin. 



Table 19. — Variation in the subspecies of Chrysothamnus greenei. 



Her- 

 barium. 



Ratio of length 

 of style-append- 

 age to total 

 branch. 



Leaves. | 



Height 

 of invo- 

 Length. Width. lucre. 



Subspecies typteus: 



Huerfano Plains, Colo., 1873, Greene> 



Twin Lakes, Colo., 1878, Jones 



San Luis Valley, Colo., Hall 11096 



La Veta, Colo., Vreeland 698^ 



La Veta, Colo., Aug. 21, 1897, CrandalP 



West Paradox, Colo., Payson 2S2Z 



Southwestern Utah, Rydberg and Garrett 9677 



Panaca, Nev., Sept. 15, 1912, Jones 



Subspecies filifolius: 



Granite, Colo., Clements 390' 



Thurber, Utah, Jones 5706 



Lund, Utah, Hall 10785 



Pancake Range, Nev., Purpus 6397 



Fish Creek, Nev., Sargent 



Gr. 

 Gr. 

 CI 



NY 

 R 

 UC 

 NY 

 UC 



NY 

 UC 

 UC 

 UC 



40.0 

 40.0 

 30.0 

 33.0 



36.4 



33.3 

 31.6 

 30.0 

 36.1 



mm. 

 3.5 

 3.2 

 2.5 

 3.3 

 3.0 

 3.5 

 2.5 

 2.8 



2.3 

 2.0 

 1.8 

 1.8 

 1.2 



mm. 

 1.0 

 1.0 

 1.1 

 1.2 

 1.0 

 1.1 

 1.0 

 0.9 



0.3 

 1.0 

 0.5 

 0.6 

 0.4 



5.8 

 6.0 

 5.2 

 6.6 

 6.6 

 5.2 

 7.0 

 6.0 



5.7 

 5.6 

 4.8 

 6.0 

 5.0 



* Type of Chrysothamnus greenei Gray. 



' Type of C. scoparius Rydberg, minor variation 5. 



' Type of C. pumUus acuminatus Nelson, minor variation 4. 

 * Type of C. filifolius Rydberg = C. greenei filifolius. 



ECOLOGY AND USES. 



Chrysothamnus greenei is a low shrub, blooming during August and September. It 

 forms a climax society in mixed prairie in the San Luis Valley, Colorado, while in Utah 

 it sometimes forms a subclimax consocies on sandy alkaline plains. It is greatly increased 

 by overgrazing, and hence is frequently associated with Bouteloua gracilis in short- 

 grass areas. 



There is no specific information at hand regarding the value of this plant. As a browse 

 shrub it is probably of about the same value as the smaller subspecies of C. viscidiflorus. 



7. CHRYSOTHAMNUS ALBIDUS (Jones) Greene, Erythea 3:107, 1895. Plate 28. 



Shrub 3 to 10 dm. high, fastigiately branched; twigs brittle, erect, congested, very 

 leafy, glabrous but very resinous-viscid, imparting a resinous stain to paper, at first 

 green and striate, later with a white smoother bark; leaves flat and 1 to 2 mm. wide 

 but drying to filiform through revolution of the margins, pungently acute, 2 to 4 cm. 

 long, 1-nerved, moderately rigid, glabrous but with a copious resinous exudate, the 

 surface with small pits ; heads in small congested cymes which are either simple or them- 

 selves loosely cymose; involucre 7 to 9 mm. high; bracts about 15, in very obscure 

 ranks, lance-oblong, all but the innermost abruptly narrowed to a long setiform usually 

 curved tip, glabrous, glutinous, the thin margins somewhat erose, the tip sometimes 

 herbaceous; flowers 5 to 6 (whitish or at least pale yellow); corolla with slender tube 

 and abruptly dilated short throat, 7 to 8 mm. long, glabrous; lobes linear, acute, 2 

 to 2.5 mm. long, erect; anther-tips triangular, obtusish, 0.2 mm. or less long; style- 

 branches exserted, the slender appendage (about 2 mm. long) much exceeding the short 

 stigmatic portion (0.5 to 1.0 mm. long) ; achenes tapering to the base, about 4 mm. long, 



