OF THE LEAVES OF BRITISH GRASSES, 329 
papillose. Cells of lower epidermis between the stereome-groups much larger than 
others. Bundles with both sheaths conspicuous. Stereome abundant, on outer side 
only ; very strong band below central bundle and smaller ones under smaller bundles. 
the latter sometimes fusing.  Chlorophyll-tissue continuous and in rings around 
bundles. 
B. Section crescentie or curved in, obvious owing to inrolling of the lamina. Stomata above only or 
(in Festuca Myuros) a few also below. Epidermal cells strongly cutinized, especially below. 
a. Stereome abundant and fusing below into thick hypodermal bands and half-girders, Section 
involute. 
ELYMUS ARENARIUS (Pl. 36. fig. 9), in upper part of leaf (see p. 330). 
A Stereome in isolated strands ; no girders. Sections crescentic. 
i. Hairs obsolete or nearly so. 
AGROSTIS VULGARIS, var. PUMILA (Pl. 36. fig. 10). Arran. June 1901. 
Ribs of two orders, midrib one of smaller. Lower epidermal cells flat. Vascular 
bundles of three orders, the larger ones in the smaller ribs. Bundles of first order 
girdered below, in midrib also above. Others have bands of stereome above and below. 
Stereome in some cases below motor cells on lower side of leaf. (See p. 335.) 
ii. Hairs long and numerous above. 
* Hairs strong aud longer than the leaf-thickness. 
FrsrvcA Myvros. Elsing, Norfolk. June 1901. 
Leaf at ribs about double the thickness it is at grooves. Motor cells nearer the midrib 
more conspicuous. Bundles of two orders; the larger have a fairly strong inner sheath. 
Stereome in feeble bands below most bundles. (See also p. 331, below.) 
** Hairs shorter than the leaf-thickness. 
KOELERIA CRISTATA (curved leaves). (See p. 331.) 
FESTUCA ELATIOR, var. ARUNDINACEA (Pl. 36. fig. 11). Hunstanton, Norfolk. July 1900. 
Upperside with few but well-marked ribs. Leaf rather thick. Lower epidermal cells 
flatter. Bundles with both sheaths well marked. Stereome forms bands above and 
below bundles; those below bundles are very broad and form an almost continuous sub- 
epidermal layer. 
II. Leaf-sections linear and many times broader than deep—i.e., lamina more or less flattened out, 
Vascular bundles, stomata, and motor cells usually numerous, and lower epidermis usually more 
strongly cutinized than upper. 
A. Ridges more or less conspicuous above ; the principal at least as high again as the thickness of 
leaf-tissue in the grooves between. 
a. Hairs present. 
i. Hairs conspicuous in number or length or both. 
* Stereome strongly developed; stomata above only. Epidermal cells very strongly cutinized, 
especially below. 
