————— 
OF THE LEAVES OF BRITISH GRASSES. 34l 
Bnowvs ERECTUS. Fulbourn, Cambs. May 1902. 
Midrib marked above and below. Cells of neither epidermis very strongly cutinized, 
those of lower rather the stronger and outer margins flatter. Bundles numerous, of 
three orders. In smaller bundles both sheaths are well seen; in larger, inner sheath is 
conspicuous, but outer is less so. Largest bundles girdered strongly above and below ; 
smaller bundles have generally no bands, occasionally girdered above. 
tt Stereome relatively scanty, or at any rate not forming true girders. 
i Motor cells absent. Chlorophyll-tissue in rings round the vascular bundles. No 
hairs. 
SETARIA VIRIDIS (Pl. 38. fig. 36). Cambridge. October 1901. 
Epidermal cells, excepting guard-cells of stomata, very large, each occupying nearly 
one-third of the depth of the cross-section. Vascular bundles very numerous and most 
of them very small. Outer sheath of bundles very well marked. The midrib with 
girder to bundle below; other large bundles have bands of stereome above and below, 
and occasionally one of the small bundles has a band above. Large mass of colourless 
parenchyma in midrib above bundle. 
A colonist, merely introduced in Britain.  Leaf-structure very peculiar among 
British grasses. 
tt Motor cells restricted to two series flanking the midrib. Chlorophyll-tissue normal. 
§ Motor-cell groups conspicuous. 
|| Large air-chambers in tissue. No hairs. 
GLYCERIA AQUATICA (Pl. 38. fig. 37). Cambs. July 1900. 
Midrib with a groove on either side; otherwise leaf-surfaces flat and parallel. Leaf 
thick and broad. Epidermal cells on both sides fairly well cutinized. Bundles large, 
of three orders; all have well-marked outer sheath, but inner is less conspicuous. 
Stereome-bands above and below bundles, also numerous small subepidermal bands on 
both sides between the larger ones. Large air-lacunze between the bundles reduce the 
chlorophyll-tissue to a few layers surrounding them. 
II No conspicuous air-cavities. Epidermis feebly cutinized. 
€ Traces of papilla. Stomata numerous on both sides. 
CATABROSA AQUATICA (Pl. 38, fig. 38). Swanton Morley, Norfolk. June 1901. 
Upperside with a few low, rounded elevations not corresponding to the vascular 
bundles. Midrib projects above and below. Some of the epidermal cells are papillose. 
Vascular bundles numerous. Stereome in fairly strong bands above and below larger 
bundles, and smaller bands above or below some of smaller ones. Chlorophyll-tissue 
rather spongy ; it is interrupted at larger bundles by bands of thin-walled colourless 
cells, which join the bundles to the stereome-bands. 
Arran. June 1901. 
Exactly as above. 
$c 2 
