10 POACEAE. 



Order 5. POALES. 



Grasses and sedges. Monocotyledonous plants, mostly herbaceous, with 

 leafy or leafless, usually simple, stems (culms), the leaves usually narrow 

 and elongated, entire or minutely serrulate. Flowers mostly perfect, small, 

 incomplete, in the axils of dry, chaffy scales (glumes) arranged in spikes 

 or spikelets. 



Fruit a caryopsis ("grain) : culm mostly hollow. Fam. 1. Poaceae. 



Fruit an achene ; culm solid. Fam. 2. Cypekaceae. 



Family 1. POACEAE R. Br. 

 Grass Family. 



Annual or perennial herbs, of various habit, rarely shrubs or trees. 

 Culms (stems) generally hollow, but occasionally solid, the nodes closed. 

 Leaves sheathing, the sheaths usually split to the base on the side oppo- 

 site the blade; a scarious or cartilaginous ring, naked or hairy, rarely 

 wanting, called the ligule, is borne at the orifice of the sheath. Inflo- 

 rescence spicate, racemose or paniculate, consisting of spikelets composed 

 of two to many 2-ranked imbricated bracts, called scales (glumes), the' 

 two lowest in the complete spikelet always empty, one or both of these 

 sometimes wanting. One or more of the upper scales, except sometimes 

 the terminal ones, contains in the axil a flower, which is usually enclosed 

 by a bract-like awnless organ called the palet, placed opposite the scale 

 and with its back toward the axis (raehilla) of the spikelet, generally 2- 

 keeled; sometimes the palet is present without the flower, and vice versa. 

 Flowers perfect or staminate, sometimes monoecious or dioecious, sub- 

 tended by 1-3 minute hyaline scales called the lodicules. Stamens 1-6, 

 usually 3. Anthers 2-celled, versatile. Ovary 1-celled, 1-ovuled. Styles 

 1-3, commonly 2 and lateral. Stigmas hairy or plumose. Fruit a seed- 

 like grain (caryopsis). Endosperm starchy. About 3500 species widely 

 distributed throughout the world, growing in water and on all kinds of soil. 

 Those yielding food-grains are called cereals. The species are more nu- 

 merous in tropical countries, while the number of individuals is much 

 greater in temperate regions, often forming extended areas of turf. 



A. Spikelets articulated below the empty scales or below a subtending involucre, or 

 attached to and deciduous with the internodes of a readily disarticulating 

 rachis, 1-flowered, or if 2-flowered the lower flower imperfect. 



1. Fruiting scale and palet hyaline, thin, more delicate than the empty scales. 



* Spikelets unisexual, the pistillate borne in the lower, the staminate in the 



upper, part of the same spike. !. Tripsacum. 



** Spikelets in pairs, one sessile and perfect, the other 

 pedicellate and sometimes perfect, more commonly 

 staminate or empty, or sometimes reduced to a 

 single scale, or wanting. 

 Axis of the racemes continuous. 2. Imperata. 



Axis of the racemes articulated. 



Raceme single : pedicels and internodes of the 



rachis club-shaped. 3. Schizachyrium. 



Racemes in pairs or more ; pedicels and rachis- 



internodes filiform. 4. Andropogon. 



2. Fruiting scale and palet never hyaline and thin, as firm 



as the empty scales, or firmer. 



1. Spikelets prickly. 5. Nazia. 



2. Spikelets not prickly, but sometimes enclosed in a 



spiny involucre. 



