OF THE LEAVES OF BRITISH GRASSES, 345 
$$ Motor cells inconspicuous. A few asperities on both sides.  Stomata more 
numerous above. 
ANTHOXANTHUM ODORATUM. Roslin. 11th May, 1901. 
Cells of neither epidermis very strongly cutinized. Vascular bundles not numerous. 
Stereome forms girders below to larger bundles, bands above and below in all cases. 
PHLEUM PRATENSE, var. NODOSUM (Pl. 39. fig. 48). Chippenham, Cambs. August 1901. 
Lower epidermal cells fairly strongly cutinized, upper less so. A very few short 
projections on epidermal cells. Bundles of three orders. Stereome forms half-girders 
below and bands above larger bundles; and bands above and below, or above only or 
below only, or none at smaller bundles. 
** No hairs or asperities ; surfaces smooth or at most slightly papillose. 
f Stereome relatively abundant, and forming girders to some or all bundles. Motor cells 
between all the ribs, and conspicuons. 
i Vascular bundles very numerous and large, and some of the motor-cell groups dipping 
more than halfway into the leaf-tissue. Stomata abundant both sides. 
ARuUNDO PHraemirtss (Pl. 39. fig. 49). Cambs. July 1900. 
Leaf-surfaces almost parallel. Leaf broad and rather thick. Epidermal cells small, 
fairly strongly cutinized on both sides of the leaf. Bundles numerous and large, of 
three orders. Outer sheath very. conspicuous in all, but inner is much less so. 
Stereome strong; it forms girders to larger bundles on both sides and to some of 
the smaller ones below. 
tt Vascular bundles neither numerous nor large; motor-cell groups not a quarter so 
deep as the leaf-section. Stomata predominate above. 
FESTUCA ELATIOR (Pl. 39. fig. 50). Fulbourn, Cambs. July 1900. 
Ribs mostly rounded; the midrib the largest, others of various orders. Lower 
epidermal cells rather flatter than upper. Bundles of three orders, corresponding to 
ribs. Inner sheath not well marked, outer more so. Most of the bundles girdered at 
least to lower side ; stereome-bands also above bundles. 
+t Stereome relatively inconspicuous, and rarely or never forming complete girders. 
Motor ceils between all ribs. 
i Motor-cell groups conspicuous. 
§ Motor-cell groups shallow and extended. | 
CxNOsURUS ECHINATUS (Pl.39.fig. 51). Royal Botanic Garden, Edinburgh. July 1901. 
Leaf rather thin. Ribs broad, rounded and low. Both upper and lower epidermal 
cells feebly cutinized and arched. Motor cells in broad bands, but individually not very 
distinct from the ordinary epidermal cells. Bundles of three orders, rather far apart. 
Sheaths not well marked. Stereome not abundant; it forms bands above and below 
most of the bundles, and girders below to larger ones. 
[Not much information as to the relationship of leaf-structure to environment can be gained from a 
comparison of the two grasses; C. cristatus is a fairly typical meadow-grass; and although the leaf- 
structure of C. echinatus differs in many features from that of C. cristatus, not one of these can be 
