118 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



4. Isachne rigidifolia (Poir.) Urban. 



Agrostis rigidifolia Poir. in Lam. Encycl. Suppl. 1: 257. 1810. "Cette plante 

 croit a Pile de Saint-Dorningue. (V. s. in herb. Desfont.)" Poiret gives as a 

 synonym Milium rigidum. The type has been examined at the Florence Herbarium. 

 It is now in the Webb Herbarium, which contains the Desfontaines Herbarium. 



Milium rigidum Poir. in Lam. Encycl. Suppl. 1: 257. 1810, as synonym of Agrostis 

 rigidifolia Poir. 



Milium rigidifolium Roem. & Schult. Syst. Veg. 2: 319. 1817. Based on Agrostis 

 rigidifolia Poir. 



Panicum rigidifolium Kunth, Rev. Gram. 1: 37. 1829. Based on Agrostis rigidifolia 

 Poir. 



Isachne rigidifolia Urban, Symb. Antill. 4: 85. 1903. Based on Agrostis rigidifolia 

 Poir. The specimen which Urban mentions, Sintenis 1359 from Sierra de Luquillo, 

 Porto Rico, is Isachne angustifolia. 



DESCRIPTION. 



Culms spreading and branching, the flowering shoots firm and rigid, 15 to 40 cm. 

 tall; sheaths glabrous, stiffly ciliate on the margin, overlapping on the flowering shoots; 

 ligule a very short, lacerate or ciliate membrane; blades oblong, 2 to 4 cm. long, 2 to 4 

 mm. wide, firm, rigidly spreading, pungently pointed, glabrous, the cartilaginous 

 margin and thick midrib whitish; panicles long-exserted, open, oblong, rather narrow, 

 2 to 5 cm. long, the branches ascending or spreading, bearing the branchlets mostly on 

 the lower side, the pedicels rigid, lto2 mm. long;spikeletsabout2mm. long, purplish, 

 borne obliquely upon the pedicels; glumes glabrous or sparsely appressed-hispidulous 

 near apex; florets smooth. 



The species is easily recognized by its smooth, rigid, spreading, pungently pointed, 

 conspicuously distichous blades. 



DISTRIBUTION. 



Mountain bogs, West Indies. 

 Santo Domingo: Rio Yaque, Fuertes 1729. 

 Leeward Islands: Guadeloupe, Duss 3190. 

 Windward Islands: Martinique, Duss 1312; Hahn 1435. 



Explanation of Plate 28.— Isachne rigidifolia. Specimen from Martinique, Hahn 1435. Natural size. 

 5. Isachne rigens (Swartz) Trin. 



Panicum rigens Swartz, Prodr. Veg. Ind. Occ. 23. 1788. "Jamaica." The type, 

 in the Swartz Herbarium at Stockholm, is an ample specimen. 



Isachne rigens Trin. Gram. Pan. 252. 1826. Based on Panicum rigens Swartz. 



description. 



Culms tufted, glabrous, slender, wiry, trailing, 1 to 2 meters long, as much as 2 mm. 

 thick, the numerous flowering shoots curving upward, 10 to 30 cm. long; sheaths 

 glabrous or puberulent, ciliate on the margin; ligule a ring of stiff hairs about 0.5 mm. 

 long; blades narrowly oblong-lanceolate, 2 to 5 cm. long, 2 to 5 mm. wide, spreading, 

 moderately firm but not stiff and rigid, scabrous on both surfaces and on the carti- 

 laginous margin; panicles ovoid or oblong, 2 to 5 cm. long, the branches and branchlets 

 stiffly ascending or spreading, the pedicels 1 to 2 mm. long; spikelets 1.8 to 2 mm. 

 long; glumes minutely hispidulous; rachilla between the two florets minutely villous; 

 palea of upper floret sparsely appressed-hispidulous. 



distribution. 



Damp shady banks, Blue Mountains, Jamaica, at 1,000 to 2,000 meters altitude; 

 also in northern South America. 



