12 POACEAE. 



Spikelets alternate; spikes remote. 29. Lcptochloa. 



tt Spikelets in open or spiki-like panicles or racemes. 

 Rachilla with hairs longer than the flowering 

 scales and enveloping them ; tall reed-like 

 grasses. 30. Phragmitcs. 



Rachilla and flowering scales glabrous. 



Flowering scales 3-nerved ; first 2 scales of 

 the spikelets empty. 

 Inflorescence of long branches, along which 

 the appressed spikelets are arranged on 

 short pedicels ; lateral nerves of the 

 flowering scales pubescent. 31. Diplachne. 



Inflorescence an open or contracted pan- 

 icle, rarely racemose ; lateral nerves of 

 the flowering scale glabrous. 32. Eragrostis. 



Flowering scales 5 many-nerved ; first 2-6 

 scales of the spikelets empty. 

 Plants not dioecious : spikelets flat, 2-edged. 33. Uniola. 

 Flants dioecious ; spikelets compressed. 34. Distichlis. 



2. Stems woody, perennial ; leaves on short branches which 



form dense whorls at the nodes. 3.j. Arthrostylidium. 



1. TRIPSACUM L. Syst. Nat. ed. 10, 1261. 1759. 



Tall perennial grasses with thick rootstocks, rather broad, flat leaves and 

 monoecious flowers. Spikelets 1-2-flowered, in terminal or axillary, solitary or clus- 

 tered, elongated spikes. Staminate spikelets in 2 's at each node of the upper part 

 of the axis, 2-flowered, consisting of four scales, the two outer coriaceous, the two 

 inner thinner, the palet hyaline; stamens 3. Pistillate spikelets in excavations 

 at the lower joints of the spike, 1-flowered; stigmas exserted; style slender. 

 Grain partly enclosed in the excavations of the spikes, covered in front by the 

 horny exterior lower scale. [Name from the Greek, in allusion to the polished 

 outer scales.] About 7 species, natives of America, the following typical. 



1. Tripsacum dactyloides L. Syst. Nat. ed. 10, 1261. 1759. 



Eootstoek 1.25-2.5 cm. thick; culms stout, erect, 1-2 m. tall. Leaves 

 smooth and glabrous, 3 dm. or more long, 1.25-3.75 cm. wide; spikes terminal, 

 and in the upper axils, solitary or 2-3 together, 1-1.25 dm. long; outer scales 

 of the staminate spikelets linear and obtuse, 8 mm. long, about 2 mm. wide, 

 faintly many-nerved; exterior scale of the pistillate spikelets horny, shining. 



Scrub-lands. Inagua : Rhode Island to Nebraska, Florida and Texas ; Hispaniola ; 

 Trinidad : Mexico : South America. Gama-grass. 



2. IMPERATA Cirillo, PI. Ear. Neap. 2: 26. 1792. 



Perennial grasses with elongated leaves, the spikelets in dense terminal 

 spike-like, silvery-hairy panicles. Spikelets 1-flowered, rarely 2-flowered, un- 

 equally pedicellate in pairs; scales 4, thin, hyaline, awnless, the 2 outer ones 

 empty, pilose, the third glabrous, usually empty, the fourth glabrous, subtend- 

 ing a perfect flower and its 2-nerved palet. Stamens 1 or 2. Styles distinct, 

 stigmas plumose. [Commemorates Ferrante Imperate, Italian naturalist of the 

 sixteenth century.] About 5 species of tropical distribution. Type species: 

 Lagurus cylindricus L. 



1. Imperata brasiliensis Trim Mem. Acad. St. Petersb. VI. 2: 331. 1832. 



Culms 8 dm. high, or less; sheaths glabrous; leaf -blades erect, 1-4 dm. 

 long, less than 1 cm. wide, the upper surface densely hirsute near the base, the 



