OF ARTS ANB SCIENCES: JANUARY 26, 1870. 191 



2. O. Watsoni, n. sp. Effuse ramosissima; foliis radicalibus spa- 

 thulatis pubescentibus ; bracteis ovatis seu ovato-lanceolatis basi tan- 

 turn soepius hinc connatis, superioribus decrescentibus lobisque involucri 

 aristis suis rigidis dimidio brevioribus. — Monitor Valley, Nevada, 

 Sereno Watson in C. King's Expedition, July, 18G8. A span to ten 

 inches high. Radical leaves an inch or more long, much broader and 

 blunter than those of the foregoing species. Lower bracts about two 

 lines long, rigid, mostly decurved, their bases commonly connate on 

 one side. Pedicels not more than half a line long, about the length of 

 the body of the involucre they support, or when apparently lengthened 

 then bibracteolate near their apex : the awns of these upper bracts 

 and of the about three-flowered involucre a line and a half or two 

 lines in length. Fruit not seen. 



3. 0. perfoliata, n. sp. Chorizanthis perfoliatce admodum similis, 

 demissa, divaricato-ramosissima ; foliis glaucescentibus (srepe rubentibus 

 in sicco chartaceis), radicalibus spathulatis, caulinis bracteisve sursum 

 vix decrescentibus (internodio dimidio brevioribus), in centro perfoli- 

 atis disciformibus subtrigono-orbiculatis venulosis triaristulatis ; invo- 

 lucris in dichotomiis sessilibus solitariis, lobis subulato-lanceolatis aristis 

 suis aequilongis. — Nevada, Fremont, second Expedition. Unionville, 

 Humboldt, and Truckee valleys, on the borders of the desert, May to 

 July, 1868, S. Watson in C. King's Expedition. A most remarkable 

 species, uniformly leafy to the tips of the branches, or only the latest 

 eauline or rameal leaves or bracts much reduced in size : these are all 

 centrally perfoliate disks, from half an inch to nearly an inch in diam- 

 eter, manifestly composed of a whorl of three wholly connate leaves, 

 the slender short awns answering to their tips ; at the first fork, how- 

 ever, there is commonly an involucre-like whorl of three or four small 

 leaves, connate only at the base. Involucre a line and a half long ex- 

 clusive of the rigid awn, which is a prolongation of a much more con- 

 spicuous costa than in the other species. Flowers from four to six, 

 conspicuously pedicellate. Perigonium pubescent, its segments ovate 

 and acute. Achenium turgidly ovate-lenticular, pointed : cotyledons 

 thickish. 



4. CENTROSTEGIA, Gray in DC. 1. c. 



Involucrum 1— 3-florum, tubulosum, 5 - 6-de'ntatum, basim juxta 

 3 — 6-calcaratum, calcaribus divaricatis dentibusque cuspidatis seu 

 aristatis. Flores, fructus, etc. Chorizanthis ; foliato et inflorescentia 



