266 



Bulletin No. 205 



[March, 



round the culm above the node; the blade (Figs. 7b and 9b) is the flat 

 portion which extends free from the stalk and is often called the leaf. 

 On the inner side of the joining of the blade and sheath is an 

 appendage called the ligule (Fig. 9c). This is usually thin and mem- 

 branous (Fig. 9c) but sometimes consists of a row of fine hairs (Fig. 

 10c), or it may be a thin membrane fringed with hairs (Fig. lie). 



The edges of the sheath are grown together in most species of 

 Bromus and Festuca, and in some other genera. Sometimes the sheaths 

 become very much inflated and inclose the inflorescence, as in Andro- 

 pogon virginicus (Fig. 24). Some species of water grasses have in- 

 flated sheaths which act as floats, as in Paspalum repens (Fig. 36). 



The blades are usually linear and very much longer than they are 

 wide (Fig. 37), but in Panicum hoscii (Fig. 91) and some other 

 species, the blades are quite broad as compared with the length. The 

 blade has a strong midrib and several nerves, or veins, on each side, 

 which are parallel to the midrib except in the broad-leaved species. 

 There are short appendages called auricles at the base of the blade in 

 some grasses. These are prominent on the leaves of wheat and barley. 

 They are also found in Hordeum and Agropyron, and other genera 

 closely related to these. 



The Inflorescence, or Flower Cluster 



The flowers of grasses are small and inconspicuous but are closely 

 grouped together and borne on shoots that are easily distinguished 

 from the leaves. The various bracts which make up the flower are 

 modified leaves. In some species of grasses the perfect flowers, from 

 which the seeds are formed, are hidden by the sheaths, as in the case 

 of some species of Panicum and in certain other genera. 



There are three common forms of inflorescence — the spike, the 

 raceme, and the panicle. The inflorescence is made up of spikelets, 



Figs. 12-16.— IL', Spiko; 1.'!, Karonio; 14, ranidc; ]5, Sj.ikelcf, (:i) first 

 glume, (b) second glume, (e) lemma, (d) palea; IG, Spikelct opened to show 

 (a) pistil, (b) stamens 



