98 leguminos^:. 



17. T. tridentatum, Lindl. Erect, 8 — 16 in. high, glabrous, neither 

 viscid nor clammy : stipules setaceously laciniate, erect: leaflets linear or 

 lanceolate, sharply serrate: heads 1 in. broad, the laciniate involucre 

 much shorter than the flowers: fl. % in- l° n g> bright purple with dark 

 centre: calyx with 10-nerved tube, the rigid segments broad at base, 

 abruptly narrowed to a subulate spinulose-tipped apex which is usually 

 subtended by a short stout tooth on each side. Var. scabrellnm, Greene. 

 Slender, with long almost filiform peduncles and broad truncate cuspi- 

 date leaflets, and a sparse scabrous pubescence upon its stalklets and 

 growing parts. — The type belongs to the seaboard, where it abounds in 

 clayey soils, both on hills and plains. The var. scabrellum is from the 

 plains of the San Joaquin. March — May^ 



18. T. obtusiflornm, Hook. Stout, erect, 1—3 ft. high, the herbage 

 bright green, sparsely short-hairy under a lens; the inflorescence and 

 growing parts somewhat resinous-glandular : stipules setaceously lacerate, 

 broad and spreading, in age reflexed; leaflets elliptic-lanceolate, 1 — \% 

 in. long, spinulose-serrate : heads more than 1 in. broad, on long stoutish 

 peduncles: calyx- tube oblong-campanulate, J£ in. long, with 10 prom- 

 in ent and as many lesser nerves, these branching and forming reticulations 

 above; teeth subulate-spinose, entire: corolla % hi. long, lilac-purple 

 with dark centre. — Common on clayey hill-sides and stream banks in 

 the open country along the base of the Mt. Diablo Eange. May. 



19. T. roscidum, Greene. Erect, with ascending branches, stout, 

 1 — 2 ft. high, stems flexuous, purple, leaves deep dull green, soft-pubescent 

 throughout and very clammy, not at all resinous: stipules spreading or 

 reflexed, setaceously fimbriate: leaflets 1 in. long, linear-lanceolate, 

 pectinately setulose : heads as in the preceding (though not glandular), 

 calyx the same; corolla white, with dark red-purple centre. — Plentiful 

 in canons, along streams, in Solano Co., etc. 



++ ++ Involucre concave,' flowers developing equally all around. 



20. T. microcephalnm, Pursh. Slender, much branched, decumbent 

 or procumbent, soft-pubescent: leaflets obovate-cuneiform or obcordate, 

 emarginate, denticulate; stipules ovate-acuminate, nearly entire; heads 

 subglobose, very small, oo -flowered, on slender peduncles; involucre 

 many-cleft, segments entire: calyx-teeth subulate, broad, scarious, and 

 sometimes toothed at base: fl. minute, pinkish: pod globose, 1-seeded. 

 — Common. May. 



21. T. microdon, Hook. & Am. Larger than the last, not rarely 

 2 ft. high, glabrous or nearly so : involucre broader, deeply cup-shaped, 

 equalling the head, its many lobes conspicuously toothed: calyx-teeth 

 rigid, triangular, acute, serrulate below. — Abundant in many places. 



