ECOLOGY OF WOODLAND PLANTS. 383 
The foliage leaves had grown considerably in each case, the 
outer fleshy scale-leaf deprived of its nutrient materials had 
collapsed, the bases of the inner leaves had thickened, and at E 
had burst the base of the wrinkled outer scale. These changes 
continued, and by April 26th, as seen at G, H, I, the outer 
scale had almost disappeared, leaving behind the usual oval bulb. 
At the base of each bulb, roots of two kinds were now formed— 
(a) several slender fibrous roots, and (b) thicker more fleshy 
roots; two of the latter are shown in G, one each in H and I. 
These elongate and thicken considerably, and become eventually 
contractile. 
DESCHAMPSIA FLEXUOSA, Trin. 
This is a characteristic grass of the dry Oak woods in the 
Millstone-Grit area and in the Coal-Measure woods over sand- 
stone. With Festuca ovina and Nardus stricta it dominates 
the dry grass-heaths, and in such exposed sunny situations forms 
dense wiry tussocks, It is much less abundant, giving place to 
-Holeus mollis, on the Coal-Measure shales, and occurs, but very 
sparingly, even on stiff clay. lt is the most extremely modified 
of our xerophytic grasses, and an excellent account of it and 
other xerophytie forms has been given by Miall (67). Its 
leaves are relatively short, wiry, permanently inrolled and nearly 
circular in transverse section, with only a narrow groove along the 
upper surface (fig. 44, p. 384). The epidermal cells of the lower 
surface are large and covered by a thick cuticle with distinct 
ridges over the wedge-shaped lateral walls (fig. 45). Beneath 
this epidermis is an almost continuous stereom, being two or 
more cells deep along the angles, the fibres of which are thick- 
walled with only a small cavity. The cells of the upper epi- 
dermis within the groove are slightly thickened, the stereom 
beneath this being confined to a narrow band jn the central 
ridge over the midrib. Two or more layers of the cells of the 
mesophyll are also thickened and pitted. The inner and radial 
walls of the endodermis are very strongly thickened, especially 
beneath the phloem, where a band for a distance of 2 or 3 cells 
on either side of the median line is two cells deep. 
When growing in the medium shade of an Oak wood this 
species has a characteristic habit. Its leaves are longer, arching 
and interwoven in such a way that the plants produce nest-like 
hollows in which humus collects. In structure (fig. 46) the 
2x2 
