CARDUACEAE. 375 



54. BIDENS L. BEGGAR-TICKS; BUR-MARIGOLD; SPANISH NEEDLES. 



Achenes flat, obovate or cuneate ; leaves or segments broad. 

 Leaves pinnately 3-5-foliolate. 



Outer bracts 4-8 ; achenes nearly black. i. B. frondosa. 



Outer bracts 10-16; achenes brown. 2. B. vulgata. 



Leaves simple. 



Heads discoid, erect ; corolla 4-toothed. 3. B. comosa. 



Heads radiate, nodding ; corolla s-toothed. 



Outer bracts not much longer than the inner ; achenes not corky on the 

 angles. 4. B. prionophylla. 



Outer bracts surpassing the rays ; achenes with corky angles. 



5. B. glaucescens. 

 Achenes linear, tetragonal ; leaf-segments small. 



Divisions of the leaves oblong or lanceolate. 6. B. Bigelovii. 



Divisions of the leaves linear. 7. B. tenuisecta. 



1. Bidens frondosa L. In wet soil from N. B. and Neb. to Fla., Tex. and 

 Colo. Alt. 4000-5000 ft. Ft. Collins; Cache la Poudre. 



2. Bidens vulgata Greene. In wet ground from Ont. and B. C. to N. C. 

 and Calif. Alt. 4000-5000 ft. Ft. Collins. 



3. Bidens comosa (A. Gray) Wiegand. (B. connata comosa A. Gray) In 

 wet ground from Mass, and Nebr. to N. J. and Colo. Along Poudre. 



4. Bidens prionophylla Greene. In shallow water and wet ground from 

 Ills, and Mont, to Colo. Alt. about 5000 ft. Poudre. 



5. Bidens glaucescens Greene. (B. chrysanthemoides and B. cernua A. 

 Gray, in part) In wet ground and shallow water from Sask. and Mont, to 

 Kans. and Colo. Alt. 4000-6000 ft. Denver; Colorado Springs; river flats 

 east of Ft. Collins; Poudre River; Table Rock; Tobe Miller's ranch. 



6. Bidens Bigelovii A. Gray. Along streams from Colo, to Tex. and Ariz. 

 Alt. up to 7500 ft. Manitou; Engelmann Canon; Como; Ute Pass. 



7. Bidens tenuisecta A. Gray. Along streams from Colo, and Ida. to Tex. 

 and Ariz. ; also in Mex. Alt. 4000-8000 ft. Engelmann Canon ; Colorado 

 Springs; Buena Vista; Palmer Lake; Ute Creek; Cimarron. 



55. THELESPERMA Less. 



Heads radiate. 



Leaf-segments linear-filiform, i mm. or less wide. 



Annual or biennial; outer bracts subulate-linear, more than half as long 



as the inner. i. T. trifidum. 



Perennial from a root-stock ; outer bracts linear-lanceolate, half as long as 



the inner or less. 2. T. tenue. 

 Leaf-segments linear, over i mm. wide ; plant perennial. 



Plant with tap-root, leafy throughout. 3. T. intermedium. 



Plant with horizontal root-stock, leafy only at the base. 4. T. subnudum. 



Heads discoid ; perennials with root-stock or woody caudex. 5. T. gracile. 



1. Thelesperma trifidum (Lam.) Britton. (T. filifolium A. Gray) On dry 

 plains from Neb. and Colo, to Kans., Tex. and N. M. Alt. 4000-6000 ft. 

 Colorado Springs; Denver, along Platte River. 



2. Thelesperma tenue Rydb. On plains and in mountain valleys of Colo. 

 Alt. 5000-9000 ft. Veta Pass; "the plains." 



3. Thelesperma intermedium Rydb. On plains, in dry or sandy soil, from 

 Neb. and Wyo. to Colo. Alt. 4000-8000 ft. Canon City; Wahatoya Canon; 

 La Veta. 



