MANUAL OF THE GRASSES OF THE UNITED STATES 



227 



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Section 1. Exxeapogox Trin. 



Spikelets 3-flowered, the first floret fertile, the second smaller, sterile, 

 the third rudimentary; awns 9, plumose. 



1. Pappophorum wrightii S. Wats. Spike pappusgrass. (Fig. 

 436.) Culms numerous, slender, decumbent-spreading, 20 to 40 cm 

 tall, the nodes pubescent; blades flat to subin volute, about 1 mm 

 wide; panicle spikelike, gray-green or drab, mostly 2 to 5 cm long, 

 sometimes interrupted below; glumes 7-nerved; lemma of first 

 floret (including awns) 4 to 5 mm long, the body about 1.5 mm long, 

 villous, 9-nerved, the awns plumose. 91 —Dry plains and stony 

 lulls, Texas to Arizona, south to Oaxaca; Peru and Bolivia. 

 Cleistogamous spikelets are produced in the lower sheaths. The 

 cleistogenes are larger than the normal florets but the awns are 

 almost wanting. The culms disarticulate at the 



lower nodes carrving the cleistogenes with them. ^4^0^ 



Section 2. Polyraphis Trin. 



Spikelets 4- to 6-flowered, the lower 1 to 3 fertile, 

 the upper reduced or rudimentary; awns 

 more than 9, scabrous. 



2. Pappophorum mucronulatum Xees. (Fig. 437.) 

 Culms erect, 60 to 100 cm tall; blades flat to subin- 

 volute, 2 to 5 mm wide; panicle spikelike, tawny 

 or whitish, tapering at summit, 10 to 20 cm long; 

 spikelets short-pediceled with 1 or 2 fertile florets 

 and 2 or 3 sterile reduced ones, the rachilla 

 disarticulating below the fertile floret and tardily 

 above it; glumes 1-nerved; fertile lemma subin- 

 durate, the nerves obscure, villous toward base, 

 dissected into numerous unequal awns 2 to 5 mm 

 long, the body about 3 mm long. % (P. apertum 

 Munro.) — Low places on plains and in valleys, 

 Texas, Arizona, and northern Mexico; South 

 America; wool waste, Maine. 



3. Pappophorum bicolor Fourn. (Fig. 438.) Culms erect, 30 to 

 80 cm tall; blades flat to subinvolute, 1 to 5 mm wide; panicle mostly 

 10 to 15 cm long, usually pink-tinged, rather loose, the branches 1 to 

 4 cm long; spikelets on pedicels 1 to 5 mm long, with 2 or 3 fertile 

 florets and 1 or 2 sterile reduced ones, all about the same height in the 

 spikelet, the rachilla not separating between the florets; glumes 

 1-nerved; lemmas somewhat indurate, obscurely nerved, pilose on the 

 callus and on the lower half to two thirds of the midnerve and margins, 

 dissected into about 12 somewhat unequal scabrous awns 2 to 4 mm 

 long, the body about 3 mm long, the awns about as long. % — Open 

 valley land, Texas, Arizona (La Nona, near Monument 111), and 

 Mexico. 



38. SCLEROPOGOX Phil. 



Plants monoecious or dioecious. Staminate spikelets several- 

 flowered, pale, the rachilla not disarticulating: glumes about equal, a 

 perceptible internode between, membranaceous, long-acuminate, 

 1-nerved or obscurely 3-nerved, nearly as long as the first lemma ; 

 lemmas similar to the glumes, somewhat distant, 3-nerved or obscurely 



Figure 438.— Pappopho- 

 rum bicolor, X 1. (Grif- 

 fiths 6291, Tex.) 



