ECOLOGY OF WOODLAND PLANTS. 385 
beneath the phloem has strongly thickened inner and radial 
walls, in sharp contrast to the remaining endodermal cells. 
Horcvus morus, Linn. 
Quick or Creeping Soft-Grass. 
This species, one of many studied by Lewton-Brain (59), is 
given by him as characteristic of waste and sandy places, but 
in the area under consideration, while it does occur in such 
situations, it reaches its maximum development in the moist 
Oak woods of the Coal-Measures, being a common associate of 
Scilla and Pteris. It extends into the Gritstone woods, where 
it competes with Deschampsia flexuosa, giving place to it in the 
drier woods and at higher levels. It is also common in open, 
sunny, dry situations such as roadsides and waste places. 
In these varied habitats it differs strikingly in form. In 
moderate shade in the moist Oak woods its leaves are broad, 
gently eurved, limp, and slightly hairy; in dry sunny spots 
they are erect, much shorter, narrower, more acuminate and 
hairy, the plant also flowers much more freely than when in the 
shade. On the steep wooded slopes when overshadowed by a 
close canopy of Sycamore or Elm, and thus brought under the 
influence of oblique or horizontal light, its leaves become longer, 
broader, thinner, much less hairy, and sharply reflexed at the 
base of the blade, the young shoot above showing a tendency to 
die early and flowers are not developed. 
Fig. 48 (p. 386) is a transverse section of the erect-leaved 
sun-form. The epidermis has a firm cuticle, short stiff hairs are 
frequent, the stomata are deeply sunk, and motor cells are well 
developed. The cells of the mesophyll are closely packed and 
contain abundant chlorophyll granules. 
Fig. 49 shows a portion of the lower epidermis, where the 
hairs are seen to alternate with relatively short epidermal cells. 
Fig. 50 shows a similar section of a reflexed shade-leaf. The 
epidermal cells are smaller and thin-walled, the stomata are not 
sunk, the chlorophyll granules are less abundant in the meso- 
phyll, and the motor cells are not so well developed. 
Fig. 51 shows a portion of the epidermis of this form. The 
epidermal cells are elongated to such an extent that the hairs 
are separated by considerable intervals; this, together with the 
act that hairs are less frequently produced, accounts for the 
very perceptible difference with regard to hairiness in the two 
