Iv] GIRDERS 69 
annua (Fig. 21), P. bulbosa, P. compressa and Dactylis 
glomerata. In Festuca ovina, F. rubra, F. heterophylla 
(Figs. 18, 27) there are groups more or less pronounced at 
the keel and margins, or even a continuous band below, 
but none above the bundles. 
Fig. 26. Transverse section of leaf 
of Nardus stricta (x about 50). 
The upper surface is repre- 
sented by the four grooves and Fig. 27. Transverse section of 
five ridges, each of the former 
with traces of motor-cells at its 
base. The deep shaded por- 
tions are sclerenchyma, strong 
girders of which join the vas- 
cular bundle of each ridge to 
the lower surface. This type 
is obviously derived from that 
in Fig. 19, and may be regarded 
as a permanently rolled leaf. 
leaf of Festuca ovina, var. 
duriuscula (x about 50), the 
type of a permanently folded 
leaf. Seven ridges and six 
intervening grooves are seen: 
each of the latter with traces 
of motor-cells below. In each 
ridge is an isolated vascular 
bundle, and a narrow scleren- 
chyma band below. 
Many grasses have an isolated band above and below 
each primary bundle only—e.g. Panicum, Cynodon—or 
above and below each of the other bundles as well— 
eg. Spartina, Arundo, Polypogon, Agrostis alba, Aira 
cespitosa (Fig. 23), Holcus lanatus, Glyceria aquatica, 
G. fluitans, Digraphis, Elymus (Fig. 25), Agropyrum 
