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.
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.
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.