PLANTiE NOY^ THURBERIANiE. 319 



PETALONYX, Nov. Gen. Loasaceamm. . 



Calyx tubo breviter cylindraceo cum ovario connato ; limbo 4 - 5-diviso, segmentis 

 linearibus tubum adseqviantibus deciduis. Petala 4-5, disci epigyni margini inserta, 

 calycis segmentis alterna, iisdem duplo longiora, decidua, longissime unguiculata ; un- 

 gui filiform! sursum marginato laminam parvam ovato-spathulatam gerente. Stamina 

 4 — 5, cum petalis inserta, iisdem alterna et longiora: filamenta capillaria: antberse 

 didymse, basi fixse, biloculares, inappendiculatse. Stylus capillaris : stigma simplex. 

 Ovarium uniloculare. Ovulum unicum, ex apice loculi suspensum, anatropum. Fruc- 

 tus parvus, utriculatus, baud angulatus, fragilis, semine obovato repletus. Testa Isevis 

 membranacea, basi chalaza orbicular! notata : endopleura tenuis. Embryonis exal- 

 buminos! cotyledones ovales, crassse, carnosse : radicula brevissima supera. — Herba 

 erecta, pube brev! cinerea aspera undique hirtello-scabra ; radice perenni ■? foliis alter- 

 nis sessilibus ovatis parvulis subintegerrimis ; floribus parvis folioso-bracteatis in capi- 

 tulas vel spicas breves ramos terminantes congestis ; petalis albidis. 



Petalonyx Thurberi. — Valley of the Eio Gila; June, 1850. — An herb of a 

 foot or two in height, probably from a perennial root, brittle ; the stems bearing nu- 

 merous short and simple flowering branches above, cinereous throughout, as are the 

 leaves, &c., with a fine and short, appressed (on the stem retrorse) pubescence, com- 

 posed of simple and sharp-pointed hispid hairs, the surface of which is shown to be 

 very rough under a lens ; thus the foliage and branchlets are somewhat adhesive in the 

 manner of Mentselia. There are no larger bristles, as in that genus. Leaves (the lower 

 fallen) three fourths of an inch long, decreasing on the branches until they become 

 only 3 lines in length, ovate or triangular-ovate, thickish, brittle in the dried state, one- 

 nerved, and with one or two rather obscure lateral veins on each side, entire or very 

 obscurely 2 - 4-toothed. Spikes or heads about half an inch long, dense ; the bracts 

 similar to the rameal leaves, but becoming pale and apparently scarious, often toothed 

 at the base, each subtending a single sessile flower, or sometimes three such flowers. 

 Bractlets 2, at the base of the decided calyx, small, linear. The flowers are stated to 

 be white or whitish, but in soaking they impart a yellow tinge to the water. Estiva- 

 tion of the calyx and corolla not determined. Calyx 2 or 2^ lines long, including the 

 slender lobes, minutely hispid ; the tube wholly connate, the limb being divided quite 

 down to the summit of the ovary. Disc small and flat, crowning the abrupt summit of 

 the ovary. Claws of the petals 2 lines or more in length, sparingly hispid outside ; 



