ECOLOGY OF WOODLAND PLANTS. 341 
lighter part of the wood, thinning out under the deeper shade 
of the less injured pines. 
The Bracken must have long been a characteristic plant iu 
this zone, as the peat, in places a foot in thickness, consists so 
extensively of the remains of this plant that we might fairly call 
it Bracken peat. 
It has, as associates, the xerophytes of the plateau, Deschampsia 
flexuosa, Calluna Erica, Vaccinium Myrtillus, &c. 
We will now apply this method to another species. 
Fig. 3 shows the distribution of Scilla festalis in Birks Wood. 
Here we see that its occurrence is only partially influenced by 
the dominant trees. It is abundant under Sycamore and Oak 
in certain areas, thinning out in others. Light was evidently 
not the only factor, so other conditions were examined. In 
certain parts of the wood, changes of soils being pretty well 
marked, an attempt was made to construct a soil-map. In fig. 4 
we have the result. The details were obtained by means of an 
augur 13 inch in diameter and with a G-inch thread to which 
iron rods were screwed. A similar borer is figured by Hall (43). 
The area was paced and borings made at intervals of 10 yards. 
The sketch-map was ruled in corresponding squares and results 
added *. As will be seen, the soil along the northern half of 
the wood consists of a shallow sandy loam resting on a bed 
of Elland flagstone quarried at the two extremities A and B. 
This area therefore is well drained, relatively dry, and the soil 
covered with only a thin layer of sandy humus; while the soils 
over the rest of the area consist of firmer, more clayey loam 
resting on a bed of clay, and in the parts indicated it is covered 
by 6 inches or more of humus. The well-known spongy pro- 
perties of humus, coupled with the fact that such fine-grained 
soils as occur here are able not only to retain, but even raise 
water above the underground level, renders this area relatively 
moist. 
On comparing this with the Scilla map, it will be seen that 
the plant is most abundant in a loamy soil covered by six inches 
or more of humus. The overshadowing trees are Oak with a 
considerable admixture of Sycamore, and it is thus an area of 
moderate shade. Along the nortbern edge of this the humus 
is very thin, on a dark sandy loam, the trees are Elm and Beech, 
* Oliver & Tansley (75) have recently given an interesting account of a 
method of surveying vegetation by means of squares, adopted by them in the 
survey of the Bouche d'Erquy. 
