

POACEAE 49 



(ligule), naked or sometimes hairy, rarely wanting, occurs at the sheath-orifice. 

 Inflorescence of spikes, racemes, or panicles, composed of spikelets, these con- 

 sisting of 2-many 2 -ranked imbricated bracts (scales), usually the lower 2, and 

 occasionally the succeeding 2-4 scales also empty, rarely all the scales flower- 

 bearing. One or more of the upper scales, except sometimes the terminal one, 

 bearing an axillary flower surrounded by a bract-like organ (palet), which is 

 placed opposite to the scale and with its back to the axis (rachilla) of the 

 spikelet, usually 2-nerved or 2-keeled and awnless, rarely 1-nerved or awned ; 

 the palet is sometimes present without the flower and vice versa ; the rachilla 

 is often thickened and appears as a hard projection (callus) at the base of the 

 scale. Flowers perfect, staminate, or pistillate, subtended by 1-3 minute 

 scales (lodicules). Stamens 1-6, rarely more, usually 3. Anthers 2 celled, 

 versatile. Ovary 1-celled, 1-ovuled. Styles 1-3, commonly 2, distinct or more 

 or less united, rarely wanting. Stigmas hairy or plumose. Fruit a seed-like 

 grain (caryopsis), sometimes nut-like. Endosperm starchy. [Gramineae Juss.] 



A. Spikelets falling from the pedicel entire (see also nos. 58, 61, 62, 68 and 76 of section B), naked, or en- 



closed in bristles or a bur-like involucre, or immersed in the internodes of a readily disarticulating 

 rachis, 1-flowered, or if 2-flowered the lower flower staminate ; no upper empty scales: rachilla not 

 extending beyond the uppermost scale. 

 Spikelets round or somewhat dorsally compressed ; empty scales manifest : hilum punctiform. 



Flowering scale and palet hyaline, thin, much more delicate in structure than the thick-mem- 

 branous to coriaceous empty scales. 

 Spikelets unisexual, the pistillate borne in the lower, the 



staminate in the upper, part of the same spike. TRIBE I. MAYDEAE. 



Spikelets in pairs, one sessile, the other pedicellate, the 

 former perfect, the latter sometimes perfect, more com- 

 monly with a staminate flower, often empty or reduced 

 to one or two scales, or occasionally wanting ; both 



spikelets pedicellate in nos. 2 and 6. TRIBE II. ANDROPOGONEAE 



Flowering scale, at least that of the perfect flower, similar in 

 texture to the empty scales, or frequently thicker and 

 firmer, never hyaline and thin. 

 Flowering scale and palet membranous. 



Inflorescence spicate: spikelets deciduous singly or in 



groups, the first scale usually larger than the rest. TRIBE III. ZOYSIEAE. 

 Inflorescence paniculate: spikelets deciduous singly 

 from the ultimate branches, the first scale usually 



smaller or narrower than the rest. TRIBE IV. TRISTEGINEAE. 



Flowering scale and palet chartaceous, cartilaginous, or 

 coriaceous, very different in color and appearance 



from the remaining scales. TRIBE V. PANICEAE. 



Spikelets much compressed laterally ; empty scales none or rudi- 

 mentary : hilum linear. TRIBE VI. ORYZEAE. 



B. Spikelets with the empty scales persistent, the rachilla hence articulated above them (below them 



in nos. 58, 61, 62, 68 and 76 and the spikelet falling entire), 1-many-flowered ; frequently the upper 

 scales are empty : rachilla often produced beyond the uppermost scale. 

 Stems herbaceous, hence annual : leaf-blade sessile, not articulated with the sheath. 



Spikelets borne in open or spike-like panicles or racemes, usually upon distinct and often long 



pedicels. 

 Spikelets 1-flowered. 



Empty scales 4 : palet 1-nerved. TRIBE VII. PHALARIDEAE. 



Empty scales 2 (rarely 1) : palet 2-nerved. TRIBE VIII. AGROSTIDEAE. 



Spikelets 2-many-flowered. 



Flowering scales usually shorter than the empty ones, 



the awn dorsal and usually bent. TRIBE IX. AVENEAE. 



Flowering scales usually longer than the empty ones, the 

 awn terminal and straight, rarely dorsal, sometimes 

 wanting. TRIBE XI. FESTUCEAE. 



Spikelets in two rows : 



On one side of the continuous axis, forming one-sided spikes 



or racemes. TRIBE X. CHLORIDEAE. 



On opposite sides of an axis which is often articulated. 



forming equilateral spikes. TRIBE XII. HORDEAE. 



Stems, at least near the base, woody, hence perennial : leaf-blade 



with a petiole-like base which is articulated with the sheath. TRIBE XIII. BAMBUSEAEL 



TRIBE I. MAYDEAE. 



Fertile spikelets imbedded in the internodes of the thick rachis. 1. TRIPSACUM. 



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