340 MR. L. LEWTON-BRAIN ON THE ANATOMY 
Roslin. May 1901. 
Exactly as above. 
[Both species of Melica are typical wood-grasses, and there are no important differences in leaf- 
structure between them. In both cases the leaf-structure seems well adapted for conditions not 
favourable to great transpiration. The minor differences between the leaves cannot, except perhaps the 
hairs of M. nutans, be recognized as adaptive.] 
** No hairs or asperities; surfaces smooth or at most slightly papillose. 
+ Stereome relatively prominent, forming girders to some or all bundles. 
i Motor cells confined to two conspicuous series flanking the midrib. Traces of papille 
above. 
Poa ALPINA (Pl. 38. fig. 33). Ben Lawers. July 1901. 
Leaf-surface parallel. Lower epidermal cells very strongly cutinized, upper much 
less so and somewhat papillose. Few or no stomata below. Larger bundles (not that 
in midrib) girdered below and with bands of stereome above; other bundles with bands 
above, or above and below, or none. In larger bundles both sheaths are well marked, in 
smaller the inner sheath is inconspicuous. Chlorophyll-tissue interrupted at larger 
bundles. 
1i Motor cells not restricted to flanks of midrib. 
§ Large groups of motor cells flanking the midrib, and smaller but conspicuous groups 
between the other ribs. No hairs. 
TRIODIA DECUMBENS (Pl. 38. fig. 34). Arran. June 1901. 
Leaf thick and quite flat above and below, except for midrib, which is sunk above. 
Lower epidermal cells extremely strongly cutinized, upper less so. Bundles fairly large, 
all with well-marked double sheath. Stereome-cells very strong. Most of the bundles 
girdered. Chlorophyll-tissue of small cells closely packed. 
[A heath-grass with a leaf that differs considerably from that typical of the group, but still fairly well 
adapted to its conditions. | 
$$ Motor cells between all the ribs alike. 
| Motor-cell groups very conspicuous. Stomata on both surfaces. 
MiLIUM EFFUsUM (Pl. 38. fig. 35). Royal Botanic Garden, Edinburgh. May 1901. 
Leaf broad. Cells of neither epidermis strongly cutinized, or with flat outer surfaces. 
Bundles far apart, of three orders. Larger bundles have both sheaths marked; in 
smaller ones inner sheath not well shown. Bundles of first order girdered above and 
below, others with only a band of stereome above. 
|||| Motor cells not conspicuous. Stomata more abundant above. 
ARRHENATHERUM AVENACEUM. Ilford, Essex. August 1901. 
No hairs. Neither epidermis has its cells very strongly cutinized. Midrib with one 
large and two small bundles, other bundles of three orders. Largest bundles strongly 
girdered to both sides, smaller ones only girdered below. 
Edinburgh. July 1901. 
Structure the same, except that some of smaller bundles are not girdered. 
