ECOLOGY OF WOODLAND PLANTS. 377 
of the rhizomes of plants growing in sandy soils containing 
'03 per cent. of lime on the Gritstone Plateau showed modi- 
fications exactly similar to those attributed by Masclef to the 
chemical influence of lime. I can find nothing in a chemical 
analysis of these soils which helps to account for these striking 
variations, but would rather attribute them to physical and 
climatic conditions. Certainly here the modifications cannot be 
attributed to the chemical influence of lime. The study of 
vegetation in this region tends to support the conclusions and 
experiments in this direetion of Warrington (103), Hedgecock 
(45), and others. 
In the moist sheltered situations over clays and shales of the 
Coal-Measures and under the shade of Beech, the rhizomes lie 
in the loose humus near the surface and may be very easily 
uprooted. Here they are relatively slender, easily break, and 
are seantily covered with brown hairs. 
Fig. 29 (p. 378) is a diagram of a trausverse section of such a 
rhizome, and fig. 30 shows in detail the structure of the mechanical 
tissues. The epidermis consists of thin-walled and wrinkled 
cells, and beneath this is a single line of dark brown cells whose 
outer and radial walls are strongly thickened and pitted. This 
is succeeded by a band 3-4 cells deep with yellowish, very 
slightly thiekened walls, these cells containing a small number 
of starch-grains. The two bands of sclerenchyma between the 
outer and inner rings of steles, consist of cells with pale brown, 
slightly thickened walls, and contain numerous stareh-grains. 
In striking contrast to this, the rhizomes of Bracken growing 
in sandy soil in an Oak-Birch wood on the Gritstone Plateau show 
an enormous development of stereom (fig. 31). The epidermis 
produces abundant hairs forming a thick felt-like covering. 
Beneath this is a band 2-3 cells deep with dark brown, greatly 
thiekened and pitted walls, succeeded by a broad yellowish- 
brown band 9-10 cells deep, and with strongly thickened walls 
forming a well-marked stereom-band containing little starch 
(fig. 32). Between this and the outer steles are several few- 
celled stereom groups. The stereom between the outer and 
inner steles forms often a complete ring and extending out- 
wardly between them. The walls are dark brown, very strongly 
thickened and pitted, the cavities greatly reduced and con- 
taining few or no starch-grains. In addition to this, each of 
the outer steles is bouuded on its outer side by a well-marked 
