80 CLASSIFICATION ACCORDING TO [CH. 



grooves. The lower girders may not fuse laterally into a 

 continuous band of sclerenchyma below (Fig. 18). 



The folded lower leaves of F. rubra and F. heterophylla come here 

 also. For the flatter leaves of F. dwriuscula see p. 78 and compare 

 Fig. 27. 



The epidermal cells in this series have sinuous thickened walls, 

 and here and there small tooth-like hairs. 



Nardus also comes here (see Fig. 26). 



(2) There are stomata below, but fewer than on the upper 

 surface. Motor-cells usually conspicuous between the 

 ridges. 



* Stronger bundles with girders of sclerenchyma 

 joining them to the epidermis, at least below. 



© Hairs sparse or none. 



Cynosurus cristatus. Mid-rib obsolete, except the 

 strong vascular bundle. Ridges low and rounded, with 

 2 — 4 flanking stomata, and well developed motor-cells 

 in furrows. Secondary vascular bundles with strong 

 girders below, the smaller bundles sheathed only and 

 isolated. Each ridge with slight sclerenchyma above. 

 A few stiff short hairs above, and the leaves are con- 

 volute. Eidges about twice the height of the leaf-thick- 

 ness between (Fig. 16). 



Agropyrum repens. Mid-rib and margin with strong 

 sclerenchyma-groups : ridges unequal, low and rounded, 

 and each vascular bundle girdered. A few pointed hairs 

 above, and motor-cells in all the grooves. A slight keel, 

 stomata on both surfaces. 



Agropyrum caninum. All the bundles have girders. 

 Slight keel. Marginal sclerenchyma. Few, very short, 

 hard, hooked asperities above and below. Eidges low. 



