GEAMINE^. 571 



dioecious. Frequently the midrib of the flowering glumes alone, or of the 

 iuteniiediate empty ones aloue, or of all the glumes, is prolonged into a 

 bristle, sometimes very long, called an aivn, and this awu is eitlier ter- 

 minal, proceeding from the point of the glume or from a notch at the top, 

 or is inserted lower down, on its back, or at its very base. Sometimes the 

 whole spikelet contains only two glumes, one empty, the other flowering, 

 with or even without a paloa, or is reduced to a single flowering glume 

 and palea. Many botanists restrict the name of glume to the outer empty 

 pair, caUing both the flowering glumes and their palea, paleas or glumellas, 

 and giving the name of sterile florets to all other empty glumes in the 

 spikelet, or even to a small prolongation of the axis which is often observ- 

 able at the outer base of the palea of the terminal flowers. The leaves of 

 Grasses are frequently described as convolute, that is, rolled inwards on 

 the edges, but this character is often very deceptive in dried specimens, for 

 in many species the leaves are perfectly flat when growing, but roll inwards 

 in drymg immediately on being gathered. 



Grasses are abundantly diffused over the whole world, from the utmost 

 limits of phsenogamous vegetation towards the Poles or on alpine summits, 

 to the burning plains of the Equator. In temperate regions they form the prin- 

 cipal mass of the green carpeting of the soil, whilst in tropical regions some 

 species (the Bamboos) attain the height of taU trees. They sujijaly us with 

 one of the most important articles of food for man, in the shape of grain, 

 and for cattle as constituting the chief portion of meadows and pastvires. 



1 f Spikelets 1-flowered 2 



t Spikelete containing 2 or more flowers 23 



r Spikelets arranged along one side of a slender, simple, linear spike 3 



2 J Spikelets arranged along one side of the simple linear branches of the panicle . . 5 

 ] Spikelets arranged in a close, cylindrical or ovate spike or spike-like panicle . . 7 

 L Spikelets arranged in a loose, branching panicle 16 



Spikelets l^flowered, in one-sided linear spikes. 



„ r Glume 1 only, ending in a fine point, and enclosing the palea and flower . 24. Waku. 



l Two outer empty glumes and a flowering one 4, 



, ("Outer glumes 1 line long, thin and obtuse. Axis not jointed . 10. Chamageostis. 



(Outer glumes 2 lines long, stifi", and strongly ribbed. Axis jointed . 23. Leptueus. 

 {. C Spikelets in pairs or clusters along the branches 3. Panicum. 



I Spikelets single along the branches 6 



( Spikelets half an inch long, laterally flattened. Glumes strongly keeled, erect. 

 6< 23. Spaetina. 



(.Spikelets about a line long. Outer glumes spreading 21. CmoDOif, 



Spikelets 'i-Jlowered, in a dense spike w spike-like panicle, 



»(■ Outer glumes without awns. Flowering glumes with or without awns .... 8 



\ All the glumes awned 13 



('Only 2 nearly equal empty glumes enclosing the flower 9 



Q 3 An additional small empty glume outside the 2 equal ones .... 3. Panicum. 

 1 Two additional small, awned, empty glumes, withinside the 2 equal ones. 

 V 5. Anthoxanth. 



Q r Outer glumes swollen and shining at the base. Spikelets rather small . 14. Nitgeass. 



\ Outer glumes keeled or boat-shaped 10 



TA tuft of hairs at the base of the flower, within the outer glumes. Keed-like grass 



10.! with a very long spike 15. Makam. 



LNo tuft of hairs outside the flower within the outer glumes. SpTkelets flat . . .11 



{Flowering glume with a fine awn on its back (sometimes shorter than the outer glume) . 

 No inner palea 9. Foxtaii,. 

 Flowering glumes without awns. Inner palea present 12 



J 2 f Keel of the outer glumes expanded into aflat wing 6. Phalabis. 



( Keel of the outer glumes not winged 8. Phleum. 



f Spikelets 3 together on each tooth of the simple, close, cylindrical spike, 1 or 2 of 



13.^ each cluster reduced to a pair of empty glumes 2C. Baelet. 



i^Spikelets small and numerous, in a close spike-like panicle, all containing flowers . 14 



