346 ECOLOGY 



deep, and moist ? (c) Is the soil covered with humus, and 

 if so, to what depth ? 



(n) What is the aspect ? and how is drainage affected 

 by slope, dip of the rocks, or other causes ? 



(12) If differences are met with in these respects, do you 

 find accompanying changes of species ? 



(13) If the wood contains a wet hollow or if a stream 

 runs through it, compare the plants (both trees and 

 undergrowth) of the wet parts with the drier parts of 

 the wood. 



(14) Compare the undergrowth of the wood with that 

 of adjacent fields. To what extent are the species 

 similar ? 



(15) How will such a comparison help to decide between 

 (a) a recent plantation and (b) an old wood ? 



Select a typical piece of woodland and mark out a narrow 

 strip across it, as indicated in Fig. 223, 1, a to b. This may 

 be subdivided into convenient squares and the parts studied 

 along the lines indicated. Afterwards a more extended 

 study may be made, and the results recorded on compara- 

 tive maps, as in Fig. 223, 1, 2, and 3, of which 1 is a tree map, 



2 a map of the common plants of the undergrowth, and 



3 a soil map. 



From studies of this kind, we learn that, by a combina- 

 tion of factors such as increased shade, a moister atmo- 

 sphere, more humus in the soil, a more regular water-supply 

 to the plants, and protection by the overshadowing trees, 

 an assemblage of plants is met with in a wood which differs 

 in many respects from the adjoining vegetation. We 

 shall also find that if trees are planted on pasture-land, 

 the undergrowth for a time will consist of pasture-species, 

 but these will eventually give place to species which can 

 better endure the shade, and the ultimate flora will be deter- 

 mined by soils, water- supply, and the other above-named 

 factors. 



