12l) MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA UNIVERSITY 



lated to the achene and at last deciduous. C)vale and seed inserted near the base of the 

 style, pendulous and anatropous. 



The genus consists of about 50 species, all natives of western North America. They 

 are all perennials, Avith a thick woody caudex or rootstock covered with brown scales. 

 The leaves are always pinnate and generally with rather numerous leaflets. In Ivesia 

 they are usually crowded and more or less overlapping. In H. pygmaea, H. Shockleyi, 

 H. Bailey i and H.saxosa,the flowers much resembles those of Slhbaldias, from which these 

 species are easily distinguished by their terminal style and pinnate leaves. The last 

 species apparently forms a transition to Potenfilla. 



KEY TO THE GROUPS. 



Filaments dilated, petaloid. 



Stamens 10. Sub-genus Euhoekelia. 



Lower stipules not dissected into linear filiform segments. 



Cyme very leafy; hpyanthium campanulate;^ bractlets ovate, much exceeding tlie sepals 



and petals. 1. Californicae. 



Cj'me less leafy; cal3'x cupulate or saucer-shaped;' bractlets not exceeding the sepals. 

 Leaves with 4-15 pairs of toothed or dissected leaflets. 

 Inflorescence truly cymose ; filaments uniform. 



Cyme many- or several-flowered; bractlets ovate or lanceolate; leaflets not 



crowded. 2. Cuneatae. 



Cyme few-flowered; bractlets linear; leaflets crowded and imbricated, silvery 

 white. 6. Sericatae. 



Cyme sub-capitate or fastigiate-corymbose; outer filaments triangular, inner ones 

 oblong-lanceolate; bractlets linear. 3. Capitatae. 



Leaves of 2-1 pairs of leaflets, which are 2-3- (seldom 5-) toothed only at the apex. 



4. Tridentatae. 

 Lower stipules dissected into linear-fiUform hairy segments. 5. Hivmtae. 



Stamens 20. 



Pistils numerous; hypanthium campanulate; sepals reflected in authesis. 



Subgenus Horkeliella. 

 Pistils 3-6; hypanthium turbinate. (^. argyrocoma in Ivesia.) 



Filaments fiUform. Subgenus Iaesia. 



Leaflets numerous, more or less crowded, often imbricated, generally divided to near the base. 

 Stem leafy (less so in /. camjje.iiri.i) ; stamens 15-20. 



Cyme corymbiform or subcapitate; petals obovate with a long claw. 8. Umjuimlatae. 

 Cyme generally open with lax branches; petals with very short claw if any, white. 



9. Eremicae. 



' In the description of the hypanthium in this genus the term eampanulale is used when the depth equals or excels the 

 diameter; mipulate or cup-shaped when it equals about ODe-hal£ of the diameter; saucer-shaped when it is equal to one-third of 

 the diameter or less; wheel-shaped when it is flat or nearly so. 



