342 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Panicle open, the branches spreading or ascending. 



Blades about 3 ram. wide, thick, rigid, pungent, with conspicuously 



thickened midrib 4. I. rigidifolia. 



Blades mostly 0.5 to 2 cm. wide, firm but not pungent nor with thick- 

 ened midrib. 



Stems trailing ; blades rarely over 5 cm. long 3. I. rigens. 



Stems clambering; blades mostly more than 8 cm. long. 



Glumes pubescent ; blades firm, not over 12 cm. long and 1 cm. 



wide 5. I. angustif olia. 



Glumes glabrous (rarely obscurely pubescent at tips) ; blades 

 mostly over 15 cm. long and 1.5 cm. wide. 

 Spikelets aggregated toward the ends of the branches and 



branchlets 6. I. arundinacea. 



Spikelets not aggregated ; panicle loosely flowered. 



7. I. disperma. 



1. Isachne leersioides Griseb. Mem. Amer. Acad. n. ser. 8: 533. 1862. 

 Tufted, straggling; culms elongate, wiry, branching; blades 7 to 12 cm. long, 



2 to 4 mm. wide ; panicles open, loosely flowered, the minute hairy spikelets on 

 flexuous but stiff gland-bearing pedicels. 



Dry cliffs and pine barrens, Cuba (Woodford, La Perla, Sierra de las Yeguas, 

 south foot of Cajalbana). The type specimen is Wright 755, from eastern Cuba. 



2. Isachne pygmaea Griseb. Fl. Brit. W. Ind. 553. 1864. 



Slender, trailing, with ascending flowering branches 12 to 15 cm. long, the 

 lower leaves bladeless, the upper with overlapping sheaths and divergent white- 

 margined blades 1 to 3 cm. long, the narrow compact panicles 1 to 3 cm. long, 

 the spikelets globose. 



Grassy banks in the Blue Mountains of Jamaica at about 1,500 meters alti- 

 tude (Cold Spring Gap, Moodys Gap). Originally described from a specimen 

 collected by Macfadyen, no locality given. 



3. Isachne rigens (Swartz) Trin. Gram. Pan. 252. 1826. 1 



Panicum rigens Swartz, Prodr. Veg. Ind. Occ. 23. 1788. 



Tufted ; culms long, slender, wiry, trailing, the numerous flowering shoots 

 curving upward, the firm divergent scabrous white-margined blades 3 to 5 cm. 

 long, 3 to 7 mm. wide, the pyramidal panicles 3 to 5 cm. long, about three-fourths 

 as wide. 



Damp shady banks, Blue Mountains, Jamaica, at 1,000 to 2,000 meters^alti- 

 tude. Originally described from Jamaica. 



4. Isachne rigidifolia (Poir.) Urban, Symb. Antill. 4: 85. 1903. 2 



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



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

 Agrostis rigidifolia. 



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



Panicum rigidifolium Kunth, Rev. Gram. 1: 37. 1829. 



Culms trailing, compressed, with short internodes throughout, branching 

 toward the end, the base simple and naked, the branches with overlapping 

 sheaths, the smooth rigid spreading pointed blades 3 to 5 cm. long, about 



3 mm. wide, with a prominent midnerve ; panicles long-exserted, about 5 cm. 

 long, 2 to 3 cm. wide. 



1 For discussion of the species confused with this by Trinius and others see 

 Hitchcock, Contr. U. S. Nat. Herb. 12: 138. 1908. 



2 For discussion of species referred to this name by Urban see Hitchcock, 

 Contr. U. S. Nat. Herb. 12: 138. 1908. 



