Trelease.] 298 [March 17, 



Stigma more or less elongated ; filaments not petaloid. 



With slender root-stocks ; stem simple, scapiform or 1-leaved, 



— T. alpinum. 

 Without root-stocks ; stem branched and leafy. 



Achenia flattened, oblique, low-nerved ; anthers elliptical, 



pointless, . . . . . — T. sparsiflorum. 



Achenia sub-terete, ribbed ; anthers oblong, mucronate, 



— T. minus. 

 * * Flowers polygamo-dicecious. 

 Perfect flowers few ; filaments spreading, not wider than the linear- 

 oblong, cuspidate anthers, . . . — T. purpurascens. 

 Fertile flowers usually with stamens ; filaments erect, spatulately 

 much widened ; anthers oval, blunt or barely mucronate ; foli- 

 age not glandular, .... . — T. polyyamum. 

 * * * Flowers dioecious (except in monstrosities). 

 Achenia usually thick-walled, not greatly flattened, filled by the 

 seed ; foliage glabrous. 

 Leaflets very thin ; fruit terete. 



Stem weak, reclining ; roots tuberous, . — T. debile. 

 Stem firmer, erect ; roots coarse, fibrous, — T. dioicum. 

 Leaflets firmer, veiny below ; fruit somewhat 2-edged, 



— T, venulosum. 

 Achenia thin-walled, 2-edged, flattened or turgid. 



Leaflets very thin ; fruit lanceolate or fusiform, scarcely ob- 

 lique, — T. occidentale. 



Leaflets firmer ; fruit broad, obliquely oval or obovoid. 



Achenia few, not reflexed ; their principal nerves parallel 

 or occasional^ reticulated, . — T. Fendleri. 



Achenia numerous, forming a dense cluster, the outer- 

 most reflexed ; with mostly free-branching veins, 



— T. polycarpum. 



1. T. clavatum,DC. Keg. Veg. Syst. Nat. i, 171. — Glabrous. 

 Stem slender but not decumbent, 6-18 inches high, sparingly 

 branched and leafy above. Leaves ample, biternate, sessile ex- 

 cept the lowermost. Leaflets thin, remote, rather large Q— 1£ in. 

 long and f-1^- in. wide), roundish, oval or obovate-cuneate, with 

 mostly three rounded apical lobes that are often again similarly 

 lobed, the sinuses rounded at bottom ; ultimate petioles equalling 

 or shorter than the smooth or slightly granular blade. Flowers 



