OF THE LEAVES OF BRITISH GRASSES. 345 
tt Motor cells inconspicuous. Stomata numerous on both surfaces. 
I Hairs long and abundant on both surfaces. 
Hocus MOLLIs (Pl. 39. fig. 42). Edinburgh. June 1901. 
Leaf broad. Midrib contains one large bundle and two smaller ones. Hairs abundant, 
but shorter than in H. lanatus. Stereome forms girders to most bundles, at least below ; 
the bands above are joined to the bundles by bands of colourless cells. The ribs become 
slightly more prominent near base of leaf. A small leaf higher up the culm of the same 
plant shows the same structure. 
Horcus LANATUS (PL. 39. fig. 43). Swanton Morley, Norfolk. June 1901. 
Low, rounded ribs of three orders; those of the first order are rather square. The 
larger bundles have girders of stereome above and below, others have no stereome above 
or below. Towards base of leaf, midrib was marked on lower side and the grooves on 
either side of it were small, and there was more stereome. 
Ilford, Essex. August 1901. 
Agrees with above description of middle of blade, but the midrib is conspicuous below 
and the grooves above on either side of it are very small. 
[As we should expect in two closely related grasses with the same habitat, there is no marked differ- 
ence in the leaf-structure. Both show well the characteristic leaf-structure of grasses of waste places.] 
tt A few long hairs above. 
BroMts MOLLIS. (See p. 333, above.) 
** Stereome inconspicuous, or at any rate not forming true complete girders, Hairs on both 
surfaces. Motor cells between all ribs. 
+ Motor-cell groups conspicuous. Stomata more numerous above. 
Lacvnus ovatus (Pl. 39. fig. 44). Royal Botanic Garden, Edinburgh. June 1901. 
Flat below. Abundant longish hairs on both sides. Stereome feeble, a few of larger 
bundles girdered, smaller ones have no accompanying bands. 
[The leaf-structure is that characteristic of the habitat, except for the rather feeble stereome.] 
tt Motor cells inconspicuous. Stomata numerous on both sides. 
HORDEUM MARITIMUM (Pl. 36. fig. 16). (See p. 331, above.) 
li. Hairs few, inconspicuous, or none. 
* Short sharp hairs or asperities present, 
+ Stereome relatively abundant, and forming girders to some or all vascular bundles. 
i Motor-cell groups conspicuous. Cutinization feeble. 
§ Sparse, short, stiff hairs below, Stomata about equal on both surfaces. 
DIGRAPHIS ARUNDINACEA (Pl. 39. fig. 45). Fulbourn, Cambs. July 1900. 
Leaf-surfaces almost parallel Ribs project very slightly both above and below. 
In the lower epidermis the cells in the grooves are larger than those covering the ribs; 
this gives to the leaf-section a curious double-faced appearance. Vascular bundles 
extremely numerous. All have fairly well-marked double sheaths. Stereome forms 
girders to larger bundles and bands above and below smaller ones. 
