GRAMINEAE. 



51 



Family 20.— GRAMINEAE. 



Flowers small, bisexual, rarely unisexual, naked, in the axil of a concave bract called 

 the flowering glume, opposite to and enclosed in which is another usually 2-nerved bract 



called the palea. The palea envelops the 



flower, which consists of a 1 -celled carpel with 



one ovule and 2 styles with feathery stigmas, 



and usually 3 stamens with versatile anthers 



The term " flower " is, however, generally under 



stood to include the flowering glume and palea 



At the base of the ovary are 2 (rarely 3) minute 



delicate bracteoles or scales named lodicules. 



Below the flowering glume and palea, and 



enclosing them more or less, are 2 (rarely 3 or 



yj » j|u' wp 4) empty bracts called the outer or empty glumes. 



"* All these together form a l-flcwered spikelet, 



-Z^gl. but there may be several flowers arranged 



-ft.gl. ^ J '^'\\W alternately on opposite sides of a common axis 



P^--^^\)j'W ?S (t^ e rhachilla) — so that the upper flowers often 



4 w z appear to be stalked — with the outer glumes 



* ' at the base, the whole forming a several- 



,, flowered spikelet ; spikelets arranged in a spike, 



r raceme or panicle. The fruit (grain or caryopsis) 



consists of the single albuminous seed and the 



^ .,„ „".,,... ... thin pericarp, which are usually inseparable. 



Fig. 18 - — Spikelet oi Ampmbromus nervosus. A , ,/ i r * ,, ,. J ., r , 



Utgl., lower empty glume ; 2nd gl., upper At the base of the g rain > and on lts anterior 



empty glume; fl. gl., flowering glume ; a, side (i.e., that which faces the flowering glume), 



awn ; pal. palea ; rhach. article of rhachilla is a sma n protuberance showing the position of 



supporting the flowermg glume. ,, , r ,-, , ■ °. •, .5 , £ . 



yy the embryo ; on the posterior side (that facmg 



the palea) is either a punctiform or linear marl? 

 (the hilum), which indicates the spot where the ovule was attached to the wall of the 

 ovary ; the hilum often lies in a furrow. 



Herbs (" grasses ") with alternate linear leaves, embracing the stem with long sheaths, 

 which are slit at maturity on the side opposite to the blade ; sheath ending at the base 

 of the blade in a tongue-like membrane (ligule), sometimes very short or reduced to hairs ; 

 stems usually hollow between the nodes. 



1. Pedicel articulate below the outer glumes, so that the ripe spikelet falls off as a whole ; 

 spikelets with 1 fertile flower. 



A. Outer glumes 2 ; inflorescence a spike or spikelike panicle. 

 B. Spikelets not awned. 



Flowering glume hard Paspalum 10. 



Flowering glume thin, 2nd glume bristly Tragus 7. 



B. Spikelets awned. 



C. Outer glumes awnless. 



Flowering glume with a terminal awn Eriochloa 11. 



Flowering glume with a dorsal awn Alopecurtjs 29. 



C. Outer glumes with long awns. 



Flowering glumo awnless Perotis 9. 



Flowering glume shortly awned Polypogon 31. 



A. Outer glumes 3. the 3rd sometimes containing a male 

 flower. 

 D. Spikelets not awned. 



E. Flowering glume hardened, usually longer than the 

 outer ones. 

 F. Spikelets bisexual. 



G. Spikelets with a bristly involucre ; panicle usually 

 spikelike. 

 H. Bristles persistant. 



Bristles several below each spikelet Setaria 14. 



Bristle 1 below terminal spikelet Cham aer aphis 1 8. 



H. Bristles deciduous with spikelets. 



Bristles slender, surrounding spikelet Pennisetum 16. 



Bristles unilateral, terminating flattened 



panicle -branches Plagtosetum 17. 



Bristles stiff, connate in lower part Cenchrus 15. 



G. Spikelets without bristly involucre ; panicle 



loose or dense Pantcum 1 3. 



F. Spikelets unisexual, in clustered spikes Spinifex 19. 



E. Flowering glume thin, usually small ; 3rd empty 

 glume thin and inconspicuous. 



