THE VEGETATION OF WOODLANDS. I 33 



closely observes the condition of the undergrowth. Further, that 

 in forming an opinion as to the value of any site for planting, it is 

 the state of the natural vegetation which gives the first impressions. 

 Observations on the low-growing vegetation of a piece of ground 

 appear thus to be of some practical value, and an attempt is made 

 here to state briefly the lessons of the ground-vegetation, and to 

 point out some limitations 



Ground- Vegetation and Soil Moisture. — The water in a soil is 

 either spring water from underground sources, or it is aerial 

 water which has fallen on the surface as rain or snow. The 

 aerial water is originally pure soft water and contains no dissolved 

 mineral matter. Spring water contains more or less mineral, 

 according to the kind of soil or rock it has passed through ; in 

 the case of limestones, which are easily dissolved, the springs 

 emerging bring hard water with calcareous matter in solution. So 

 far as plants are concerned, soft water does not aid so much in 

 nutrition as water which carries mineral salts. Places where 

 springs emerge are therefore frequently well-marked, and may be 

 distinguished easily in a wood or on a hillside by brighter green 

 patches. The green colour is due to a more abundant supply 

 of water in movement, so that it brings to the plant-roots both 

 food-material and air. Constant springs are generally indicated 

 by a deep carpet of mosses and water-loving plants, with willows 

 and alder as natural trees. Springs which only flush the ground 

 now and then, as in spring or after rains, are frequently dry under 

 foot, and they give rise to a drier vegetation, particularly grasses 

 and sometimes bracken. When the green patches are sharply 

 defined against a darker vegetation, it is either a sign that the 

 spring water has sunk into the soil again or that it has ceased 

 to flow and has become stagnant. The presence of surface 

 springs in a wood shows that -the tree-roots are supplied with 

 water. If no springs are visible, the surface soil obtains its 

 supplies of water mamly from the air, and in such soils there 

 is always a risk of the upper layers becoming leached, that is, the 

 soluble mineral matter is carried down into the deeper layers 

 of the soil. This washing out rarely extends deep enough to 

 affect the roots of old trees, but when it occurs the ground- 

 vegetation soon becomes scanty, and if young trees are planted 

 they make little progress till their roots reach the richer layers 

 below, a frequent experience on heathy soils. The risk of surface 

 impoverishment is modified by the action of springs, which not 



