GRAMINEAE 



inflorescence grade imperceptibly into each other. The axis and branches of a 

 panicle and the rachis of a raceme or spike may be as elaborately modified and 

 specialized as may be the parts of a spikelet. The axis, rachis, or branches may be 

 continuous (not jointed), or articulate (jointed) and usually disarticulating (breaking 

 up). The breaking up takes place at definite points and has to do with scattering the 

 seed. The point of disarticulation is the same in grasses of the same kind (or genus) 

 and is usually alike in related genera, and for this reason is of great importance in 

 the classification of grasses. When there are no joints in the axis or branches, the 

 disarticulation comes in the spikelet, either above the glumes and between the florets 

 or below the glumes. 



Spikelets differ in the number of florets (1 in Agrostis, to many in Eragrostis); 

 the parts vary in relative size; the rachilla- joints slender or thick, short or long; the 

 node at the base of the floret (callus) sometimes prolonged into a sharp point, as in 

 Aristida and Stipa. Glumes may be very large as in wild oats, or reduced to rudi- 

 ments or suppressed as in most species of Paspahtm. Lemmas are so characteristically 

 modified that they form one of the principal distinguishing characters for identifying 

 genera and species and are so used in the keys. 



The arrangement of spikelets in the inflorescence is as important as are the 

 variations of spikelets themselves. They are borne pediceled (that is on a pedicel or 

 footstalk) or sessile (without a pedicel), in leafless panicles (Festuca, Poa, Eragrostis), 

 racemes (Andropogoneae) (Fig. J) or spikes (Hordeae) (Fig. I, c). 



The tribes are largely based on a combination of the structure of the spikelet and 

 the structure of the inflorescence. 



1. Bamboo Tribe (Bambuseae)— Woody plants of great size; culm sheaths very 

 large, their blades much smaller, not petiolate; leaf sheaths much smaller, their blades 

 petiolate, elongate. 



2. Fescue Tribe (Festuceae)— Spikelets 2-to many-flowered, the inflorescence 

 (mostly less specialized than in the other tribes) in open to dense panicles, contains 

 the greatest number of genera and is the most widely distributed. 



3. Oat Tribe (Aveneae)— Like Festuceae but glumes enlarged, florets fewer, 

 mostly awned from the back; Avena (the oat) the most important genus. 



4. Fingergrass Tribe (Chlorideae)— Spikelets 1-to-several-flowered on one side 

 of a continuous rachis; inflorescence of 2- to several 1-sided spikes, these few to 

 several, racemose or digitate; Kou Ya Ken Shu Cynodon, the commonest genus. 



5. Barley Tribe (Hordeae)— Spikelets sessile on a simple axis; the rachis, rather 

 than the spikelets specialized. The cereals, wheat, barley and rye, belong to this 

 relatively small tribe. 



6. Bentgrass Tribe (Agrostideae)— Spikelets 1-flowered; inflorescence an open 

 to spike-like panicle, the spikelets awned or awnless, conspicuously awned in Stipa 

 and Aristida. 



7. Chieh Lu Ts'ao Ts'u (Zoysiae)—A single genus, Zoysia, with only two species 



in our flora. Spikelets nearly sessile in a single short spike, the spikelets falling 

 entire; first glume wanting, the second glume firm, pointed; a low densely tufted 

 perennial. 



8. Yi Ts'ao Ts'u. (Phalarideae)— Spikelets with one perfect floret and two 

 sterile florets below (minute in our one genus, Phalaris); panicle pale, spike-like. 



9. Rice Tribe (Oryzeae)— Spikelets with one perfect floret, laterally compressed, 

 in terminal panicles; annual or perennial swamp grasses. Oryza, rice, is the most 

 important genus. 



4?,3 



