The asclepias lanceolata is allied to the asclepias longifolia and viridiflora by the absence of appendage or horn of the nectary. It is distinguished from the longifolia, which is characterized by alternate linear leaves, and umbels erect. [Illustration: _Asclepias lanceolata._] The asclepias lanceolata and asclepias viridiflora belong to Mr. Elliott's genus acerates. In both, the nectary or stamineous crown is short concave, and oppressed to the angles of the filaments. ART. VIII. _Description of a New Genus of American Grass._ DIPLOCEA BARBATA, by C. S. RAFINESQUE, Esq. Diplocea. _Generic definition._ Flowers paniculated monoical or polygamous. Exterior glumes membranaceous bivalve one to three flowered, valves subequal emarginated mutic. Anterior glumes bivalve unequal, the largest notched, notch aristated, the smallest mutic entire bearded. _Additional characters._ Flowers when single sepile with a lateral jutting peduncle, when double, one sepile and one pedunculated, when three two are pedunculated and alternate. The hermaphrodite and male flowers are similar: the female are nearly clandestine, inferior. Stamens 3, styles 2. Seeds ovate oblong. _Observations._ This genus is intermediate between _amphicarpon_, Raf. (_Milium amphicarpon_, _Pursh_) and _aira_, L. It differs from this last by its polygamy, variable number of flowers, notched valves, &c. The generic name means _double notch_. Its type is the following species, which had been ranged with the _aira_, by Walter, and considered doubtful by Pursh. _Diplocea Barbata._ _Specific definition._ Stems cespitose, articulations bearded; leaves rough glaucous, neck ciliated; panicles, few flowered, female axillary; largest valvet rinervate, and ciliated as well as the awl. _Latin definition._ Caulibus cespetosis, geniculis barbatis, collo ciliato, foliis scabris glaucis, paniculis paucifloris, femineis axillaribus; valva majore trinerva, aristaque ciliata.