TN 
OF THE LEAVES OF BRITISH GRASSES, 331 
** Stereome inconspicuous or in isolated strands, but not forming girders. Epidermal cells 
strongly cutinized below, less so above. 
t Motor-cell groups conspicuous. Very hairy both sides. Stomata above only. 
KOoELERIA CRISTATA (Pl. 36, fig. 15). Royal Botanic Garden, Edinburgh. June 1901. 
Thickness of leaf at ridges about double that at grooves. Larger ribs square, others 
rounded; a few very low. Bundles of three orders, larger ones in ribs, and one or two 
of the smallest between these. Largest bundles have strong inner sheaths. Stereome 
takes the form of thin plates (one cell thick) within the epidermis. 
Gullane, Haddington. June 1901. 
Exactly as above, but smaller and less hairy. 
[The leaf-structure shows a higher degree of xerophily than is usual in pasture-grasses, and the grass 
is capable of growing under somewhat xerophilous conditions.] 
tt Motor cells inconspicuous. 
I Hairs and numerous stomata on both sides. 
HORDEUM MARITIMUM (Pl. 36. fig. 16). Hunstanton, Norfolk. August 1901. 
Low, rounded ribs above. Bundles few, of two orders; central bundle alone with 
marked inner sheath. Stereome forms feeble bands above and below some of the 
bundles. 
tt Hairs on upperside only. 
§ Hairs short, stiff, and rather sparse. 
FESTUCA RUBRA. Bridge of Allan. May 1901. 
Lower leaf. Midrib obsolete. Rather sparse and short hairs above, none below. Lower 
epidermal cells flat, upper arched. Bundles of two orders, larger ones with well-marked 
inner sheath. Bands of stereome above and below bundles. (See also p. 328.) 
Festuca Myuros, var. BROMOIDES. Edinburgh. May 1901. 
Ribs few on upperside. Hairs on upperside of ridges rather short, but strong. 
Stereome feeble, bands below stronger bundles and some above. 
[In contradistinction to the species of Poa those of the genus Festuca possess leaves which show a 
considerable amount of structural differentiation. The two wet meadow species, F. elatior and pratensis, 
possess a leaf-structure which is fairly characteristic of meadow-grasses. Comparing with these the leaf- 
structure of F. Myuros and its variety bromoides from sandy places, we notice that no very eg 
structural modification has taken place. The leaves are much smaller, and dependent upon this the 
stereome is considerably less abundant. Hairs are developed upon the upper surface, and there is a 
greater difference between the lower and the upper epidermis in the cutinization and in the number of 
stomata; these differences all point to a greater degree of xerophily. The small amount of stereome 
present on the upperside of the leaf indicates a slight approach to the heath-grass type of leaf- 
structure. 
F. arundinacea, a variety of F. elatior, again shows an approach to the maritime type of xerophilous 
leaf-structure. The ribs have become more prominent and are covered with numerous hairs; the cells 
of the lower epidermis are strongly cutinized and have a flat outer surface, while the oe T confined 
to the flanks of the ridges: all these differences show a high degree of xerophilous modification. The 
SECOND SERIES.—BOTANY, VOL. VI. 3B 
