320 PLANTS NOV^ THURBERIANyE. 



their lamina less than a line long, ovate, sometimes appearing subcordate by the inflec- 

 tion of the margins .of the claw at its summit, but when explanate it is found to be 

 ovate-spatulate, with a tapering base, the surface minutely veined. Filaments attaining 

 the length of half an inch, glabrous : anthers small, with no apparent connective. 

 Style resembling a filament, terminated by a minute and simple stigma. Ovary not 

 ribbed, angled, nor appendaged, ripening without much change, or any considerable en- 

 largement, into a thin and fragile hispid-scabrous utricle, 1^ or 2 lines long, from which 

 the calyx-lobes fall, and which at length breaks in pieces irregularly. Seed filling the 

 cell, obovate, pointed at the hilum, smooth. Cotyledons thick, plano-convex; radicle 

 short, acute. 



Botanists will recognize in this plant a very interesting addition to the tribe or sub- 

 order Gronoviece, composed of those Loasacece which have the ovules reduced to a 

 single one, suspended from the summit of the cell, and the seed destitute of albumen. 

 The present genus is especially remarkable for the very long-clawed petals ; from which 

 character the name is derived. It forms in some respects a connecting link between 

 Gronovia and Cevallia ; while the anthers are those of a Mentzelia. Professor Fenzl 

 would probably recognize the petals of Petalonyx as homologous with the inner series 

 of the perianth of Cevallia^ unless, indeed, on comparing them with the stamens of the 

 latter genus, surmounted by petaloid tips, these slender petals were regarded as an ex- 

 ternal series of stamens transformed into staminodia. But I can draw no line of dis- 

 tinction between true petals and an external series of sterile, anantherous stamens, 

 alternate with and next within the sepals. 



EEEMIASTRUM, Nov. Gen. Compositarum. 



Capitulum multiflorum, heterogamum, heterochromum ; fl. radii uniserialibus ligu- 

 latis foemineis ; disci tubulosis hermaphroditis. Involucri subbiserialis squamae lineari- 

 lanceolatEe, laxse, sequilongse, foliacete, marginibus hyalinis fimbriatis alatae. Recepta- 

 culum hemisphsericum, nudum. Ligulse circiter 20, elongatse. Corollee disci subcylin- 

 dricse, tubo proprio brevissimo, limbo 5-lobo. Styli rami plani, appendice brevissima 

 obtusissima. Achenia compressa "? hirsuta, binervia. Pappus in radio et disco con- 

 formis, brevis, duplex ; exterior e paleis 10 - 12 oblongo-cuneatis setoso-palmatifidis ; 

 interior e setis totidem rigidis scabris insequalibus, nempe, 5-6 paleas bis superantibus 

 coroUee disci dimidio brevioribus, et 5 - 6 alternis minoribus. — Herba pumila, mono- 

 carpica, cinereo-hispida ; foliis alternis lineari-spathulatis ; ramis capitulum majuscu- 

 lum basi foliosum gerentibus ; ligulis albis. 



