STANDLEY — TREES AND SHRUBS OF MEXICO. 65 



7. POACEAE. Grass Family. 

 (Contributed by Prof. A. S. Hitchcock.) 

 Rb:ference: Hitchcock, Mexican grasses in the U. S. National Herbarium, 

 Contr. U. S. Nat. Herb. 17: 181-389. 1913. 



Herbs or rarely shrubs or trees; leaves usually long and narrow, but in the 

 woody species usually lanceolate or elliptic, often petiolate; -flowers small, 

 greenish, or purplish, arranged in small spikelets, the spikelets in narrow or 

 open panicles ; fruit a caryopsis or grain. 



Most of the woody grasses belong to the tribe Bamboseae, usually known in 

 English-speaking countries as bamboos. In tropical America there are few 

 .grasses, aside from bamboos, that have woody stems, and nearly all of these 

 belong to the genus Lasiacis of the tribe Paniceae. 



It is impracticable to draw a sharp distinction between woody and herba- 

 ceous grasses. In the following account only those species have been included 

 which possess culms that persist from year to year. Some excluded species 

 have woody crowns or have the base of the culms woody ; others, such as the 

 sugar cane and reed (Phragmites communis Trin.), have large firm culms that 

 appear woody during the season of growth, but do not persist. 

 Leaves many times longer than broad; panicle a large terminal plume; spikelets 

 2 to several-flowered, more or less silky. 

 Spikelets unisexual, the pistillate long-silky, the staminate glabrous; plants 



dioecious 1. GYNERIUM. 



Spikelets perfect, the lemmas silky 2. ARUNDO. 



Leaves lanceolate or elliptic, usually not more than 20 cm. long ; panicles narrow 

 or open but scarcely a large plume ; spikelets 1 to several-flowered. 

 Spikelets unisexual ; pistillate spikelets borne on the upper branches and on 

 the ends of the lower branches of a loose terminal panicle, the smaller 

 staminate spikelets pedicellate along the lower branches; leaves asym- 

 metrically lanceolate-oblong, the larger 20 cm. long and 5 cm. wide. 



3. OLYRA. 

 Spikelets perfect (often with sterile florets above or below) ; leaves usually 

 less than 5 cm. wide. 

 Spikelets globose or ovoid, obtuse, with one perfect terminal floret and a 



sterile floret below; blades sessile 4. LASIACIS. 



Spikelets 1 to several-flowered, the florets acute or acuminate ; blades 

 usually contracted into a short petiole and jointed with the sheath. 

 ( Bamboos. ) 



Stamens 6. Spikelets several-flowered 5. BAMBOS, 



Stamens 3. 



Spikelets 1-flowered 6. CHUSQXJEA. 



Spikelets 2 to many-flowered. 

 Glumes 1 or 2 ; sterile lemmas none ; spikelets loose, many-flowered, 



elongate, paniculate or racemose 7. ARUNDINARIA. 



Glumes 2 ; sterile lemmas 1 or 2 ; spikelets in racemes or 1-sided 

 spikes, these arranged in tufts at the culm nodes. 



8. ARTHROSTYLIDIUM. 



1. GYNERIUM Humb. & Bonpl. PI. Aequin. 2: 112. pi. 115. 1809. 

 1. Gynerium sag'ittatum (Aubl.) Beauv. Ess. Agrost. 138. pZ. 24. f. 6. 1812. 



Saccharum sagittatum Aubl. PI. Guian. 1: .50. 1775. 



Gynerium saccharoides Humb. & Bonpl. PI. Aequin. 2: 112. pi. 115. 1809. 



River banks and low ground, forming dense colonies, Veracruz and Oaxaca. 

 West Indies to South America, the type from French Guiana. 



