GRASS FAMILY. 



27 



mostly 2-keeled, the inflexed margins enwrapping the flower. 

 Within and at the base of the bractlet are 2 (rarely 1, 3 or more), 

 usually minute organs (the scales) which are sometimes considered as 

 representing additional rudimentary bractlets, sometimes as the parts 

 of a rudimentary perianth; the scales at the time of anthesis become 

 turgid, pushing the bractlets and palea apart, thereby allowing the 

 anthers and stigmas to protrude; after anthesis they lose their turges- 

 cence, becoming hyaline, and allow the bractlet and palea to close 

 again. Perianth obsolete, unless represented by the scales. Stamens 

 usually 3, rarely 1, 2, 6 or more, hypogynous; filaments capillary; 

 anthers 2-celled, mostly versatile and pendulous at maturity, usually 

 proterandrous. Ovary superior, 1-celled. Styles usually 2, free, or 

 more or less united below, or obsolete; stigmas 2, widely branched and 

 usually plumose, covering a large area and thus specially arranged to 

 catch pollen carried by the wind, usually spirally branched, rarely 

 barbellate with papillate cells. Ovule 1. Fruit in ours an achene, 

 often adnate to the palea and sometimes also to the bractlet. Seed in 

 ours adnate to the pericarp. Embryo small, outside the base of the 

 endosperm. 



KEY TO THE TRIBES. 



A. Spikelets l-flo\vered, the flower perfect; or with 1 perfect flower and 1 

 (rarely 2) empty bractlets or staminate flowers bslow (rarely above) it. Dice- 

 cious species and species with 2 or more perfeci flowers should be looked for 

 under B. 



Both bractlet and palea cartilaginous, coriaceous or chartaceous (at least dis- 

 tinctly firmer in texture than the bract-) and becoming indurated in fruit. 

 Rachilla jointed below the bracts so that the spikelets fall from the pedicel 

 entire; spikelets terete, or flattened on the back only, not at all laterally 

 compressed; either strictly 1-flowered or the perfect flower subtended by 1 

 (never more) empty bractlet or staminate flower; lower bract often herba- 

 ceous and usually much the smaller 2. Panick.k, p. 29. 



Rachilla jointed above the bracts so that these remain after the flowers fall 

 away; spikelets laterally compressed on both sides; subtended by 2 

 (rarely only 1) sometimes minuie, empty bractlets or staminate flowers; 



bracts usually sub-equal 3. Phalaripe.e, p. 33. 



Only the bractlet firmer in texture than the bracts and becoming indurated in 

 fruit; palea hyaline. 



Awn terminal, geniculate; bractlet cylindrical-involute:— Stipa in 



4. Agkostide.e, p. 37. 

 Awn dorsal, geniculate; bractlet not cylindrical-involute:— sometimes Avena 



in 5. Avene.e, p. 48. 



Neither bractlet nor palea firmer In texture than the bracts, though in Hordese 

 both may be equally firm; often one or both of them hyaline. 

 Spikelets pedicellate; arranged in lax or more or less dense and spikelike 

 panicles or racemes; if in racemes or spikes these sometimes densely 

 cylindrical but the spikelets not in distinct rows. 

 Spikelets of two kinds in the same inflorescence, one polygamous the others 

 imperfect or rudimentary; two (one of each kind) of several at a node. 

 Spikelets in pairs, or the terminal in threes, at e ich node of the jointed 

 rachis, one (or two) pedicellate and (in ours) imperfect, the other 

 sessile and containing 1 perfect flower subtended by either a hyaline 

 empty bractlet or a staminate flower. . . . ]. Andropogone.k, p. 28. 

 Spikelets crowded at each node of a dense, 1-sided, brush-like panicle: the 

 fertile solitary, short, terminating the panicle-branches and entirely 

 concealed by the long sterile spikelets, which consist of about 10 



empty bractlets:— Lamarckia in 7. FESTUCE*. p. 57. 



Spikelets all of one kind in the same inflorescence; though their contained 

 flowers may be perfect, monoecious or polygamous. 



