OP ARTS AND SCIENCES. '217 



this genus the ambiguous little plant named Prenanthes ? exigua in PI. 

 "Wright, 2, p. ] 05. There is another and less incongruous annual or 

 biennial species, with almost as white pappus, to be added. Well 

 marked as the genus is in habit and flowers, it may be divided into 

 nearly as many sections as there are species. The differences are 

 exhibited below.* The genus differs from 



Stephanomeria essentially in the pappus only, and both genera have 

 nearly the same geographical range, being characteristic Compositse of 

 our dry interior region. There are so few characters to hold to in the 



* LYGODESMIA Don, Torr. & Gray. 



§ 1. Perennes, junciformes; involucro tantum calyculato ; pappo moUi sordes- 

 cente. [Lygodesmia & Erythremia Nutt.) 



1. L. juNCEA Don. The original species. Heads about half the size of those 

 of the next. 



2. L. GRANDiFLORA Torr. & Gray. FoHosa; foliis graminoideis seu dianthoi- 

 deis integerrimis. — To this belongs L.juncea of Durand's Utah Memoir, and 

 the var. dianthopsis of Eaton in Bot. King, p. 200. 



3. L. APHTLLA DC, cum var. Texana Torr & Gray. Caulibus totis vel 

 superne apliyllis ; foliis dum evolutis ssepe pinnatifido-laciniatis. — L. juncea 

 Gray, PI. Wright, 1, p. 129, no. 417, is an usually branching and more leafy form 

 of this species. 



§ 2. Perennes ? divaricato-ramosissimEe ; ramis spinescentibus ; involucri squa- 

 mis extefioribus gradatim brevioribus ; pappo rigidulo sordido. (§ P/eia- 

 canthus Nutt.) 



4. L. spiNOSA Nutt. Perhaps only biennial ; the crown producing a remark- 

 able woolly tuft. 



§ 3. Annuae seu biennes ; caulibus paniculatis ; involucro tantum calyculato ; 

 pappo moUi albo vel albido. 



6. L. ROSTRATA. Bi-tripcdalis, erecta, ramis adscendentibus laxe polyceph- 

 alis ; foliis angustissime linearibus elongatis, ramealibus in bracteas subulatas 

 decrescentibus ; pedicellis squamoso-bracteolatis ; involucri 8-9-fiori squaniis 

 propriis totidem angustissime linearibus elongatis ; acheniis gracilibus apice sub- 

 rostratim attenuatis. — L.juncea var. rosfrata Gray, in Proc. Acad. Philad. 1863, 

 p. 69. A good specimen of this, collected at Greeley, Colorado, in sandy soil, 

 by E. L. Greene in 1872, shows the character of the root, akenes, and pappus, 

 which mark it as wholly distinct from L.juncea. 



6. L. EXIGUA. Spithamaja, a basi divaricato-ramosissima ; foliis radicalibus 

 spatlmlatis runcinato-subpinnatifidis, caulinis raraealibusque sensira in bracteas 

 ovato-subulatas minimas decrescentibus ; pedicellis subnudis ; capitulis parvis ; 

 involucro 4— 5-floro e squamis totidem lineari-oblongis cum bracteolis brevissimis 

 1-2; acheniis breviusculis columnaribus ab apice truncate deorsum parum 

 angustatis inter costas 5 latas scabriusculas angustissime sulcatis. — Prenanthes f 

 exigua Gray, PI. Wright, 2, p. 105. CoUected only by C. Wright, in 1852. 

 VOL. I. 28 



