72 BOTANY. 



POTENTILLA ANSERINA, Linn. Sp. 1, p. 495; Torr. & Gray, Flor. 1, p. 444. Shores of Klamath 

 lake, 0. T. 



POTENTILLA FLABELLIFOLTA, Hook.; Torr. (6 Gray, Flor. p. 442. Cascade mountains, 0. T. ; 

 altitude 6,000 feet. 



POTENTILLA GRACiLis, var. FLABELLiFORMis, Torr. & Gray, Flor. p. 440. McCumber s, N. Cali 

 fornia, and Klamath basin. 



POTENTILLA RIQIDA, Nutt. in Jour. Acad. Philad. 7, p. 20. Banks of Hat creek, N. California. 



POTENTILLA GLANDULOSA, Lindl. Bot. Reg. t. 1583 ; Hook & Arn. Bot. Beech., p. 338. Banks 

 of Hat creek, N. California. 



IVESIA, Nov. Gen. (Torr. & Gray.) 



&quot; Calyx 5-fidus et 5-bracteolatus, tubo concavo vel campanulato. Petala 5, oblongo-cuneata 

 vel obcordata, decidua. Stamina 20, bi triseriata, tubo calycis, vel tantum 5 rnargini disci 

 tenuis, inserta ; filamenta filiformia vel subulato-filiformia, persistentia. Ovaria plura vel 

 plurima, receptaculo conico villoso insidentia : ovulo pendulo : stylus infra-apicalis, gracilis, 

 articulatione deciduus : stigma simplex. Achenia leevia. Radicula supera. Herbfe Horkeli. B 

 facie, plurifoliolatas, albi florae, in sectionibus 2 disponendas, nempe : 



&quot;1. HORKELIOIDES. Perennes, e caudice crasso confertissime multifoliolatse ; floribus con- 

 gestis subsessilibus ; calycis 5-fidi tubo campanulato vel turbinato ; petalis spathulatis parvulis ; 

 acheniis Irevibus paucis (ovariis 6-12 ?) Species duo : I. GORDONI, (Horkelia Gordoni, Hook. 

 Kew. Jour. Bot. 5, p. 341, t. 12, H. ? multifoliolata, Torr. in Sitgreaves, Zuni Exped. p. 159.) 

 I. PICKERINGII, N. California ; Coll. Expl. Exped. 



&quot;2. POTENTILLOIDES. Annue, laxe plurifoliolatte, laxifloraa, pedunculis ebracteatis ; calyce 

 concavo (bracteolis conformibus) subasqualiter fere 10-partito ; acheniis plurimis grosse pauci- 

 costatis. Sp. 1, nempe: 



&quot;I. GRACILIS, (sp. nov.) : gracilis, laxe villosa ; foliis radicalibus 11-21-foliolatis; foliolis infe- 

 rioribus 3-5-partitis breviter petiolulatis, summis plerumque alte bifidis subconfluentibus, 

 segmentis lineari seu oblongo-spathulatis, caulinis parvis cum foliolis 5-9 subintegris ; floribus 

 parvis in cyma effusa sparsis ; pedunculis ebracteatis filiformibus mox cernuis ; petalis 

 obcordatis calyce longioribus; stylis inferne vesiculoso-subincrassatis. Banks of Rhett lake, 

 one of the Klamath group. A foot high, producing many slender and nearly erect stems from 

 a slender and evidently annual root. Leaflets thin, 3 to 6 lines long, irregular, often alternate, 

 the lower ones rather sparse. Branches of the open cyme, as well as the peduncles, very 

 slender ; the latter fully an inch long. Flowers very small ; the calyx, when spread out flat, 

 only about 4 lines wide, flattish, and open like that of a Potentilla ; the accessory lobes like 

 the real sepals, only slightly smaller and blunter. Petals white, broad, deciduous. Stamens 

 20, in three ranks, five of them, viz : those opposite the true sepals inserted on the margin of a 

 narrow and thin patelliform perigynous disk, (which is villous, like the receptacle it surrounds,) 

 the others borne on the face of the calyx, the five opposite the petals inserted very close to the 

 disk, but distinguishably separate from it ; the remaining ten inserted higher up, just below 

 the 10 sinuses, and answering to them, but in reality borne one on each side of the base of each 

 interior or true division of the calyx ; the persistent filaments slightly dilated at the base. 

 Receptacle conical, hirsute. Ovaries indefinite, 30 or more, inserted by the inner angle just 

 above the base ; the style inserted a little below the rounded apex by a narrow base, above 

 which it is more or less enlarged and glandular, or rather vesicular, and tapering gradually to 



