I 34 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



only bring up water, but also carry up the lower soil and gradually 

 spread it over the surface. On light sandy or heathy soils, where 

 surface leaching is liable to occur, benefit would thus result if 

 any springs or streams which may be present were made to run over 

 the surface as far as possible. Generally, however, in our climate, 

 and on the " till " soils, spring water accumulates and becomes 

 harmful to trees if not kept moving by artificial drainage. The 

 ground-vegetation soon indicates undrained places, while it also 

 tells something of the kind of water. Tall herbage such as 

 rushes, sedges, tussock grass {Ai'ra caes^itosa), queen of the " 

 meadow {Spiraa) diwd marsh marigold {Caltha) show excess of 

 spring water injurious to trees, but the fact that the place carries 

 a tall, quick-growing herbage indicates that the substratum 

 contains more soil than peat and will be fertile if drained. Bog 

 moss {Sphagnum) is a sign of too much water, and if tall plants 

 are absent it generally means that the water is soft and acid ; 

 such a spot will only be suitable for such trees as birch or spruce. 

 It is the beginning of a bog-vegetation, including plants like 

 cotton-sedge, heather, pink bell-heath, sweet gale, and not suited 

 for trees except after careful drainage. 



Ground- Vegetation and Degeneration of Woods. — A wood does 

 not remain always the same ; it is either progressive, advancing 

 more and more to the condition of closed wood, or it is 

 degenerating and going back to scrub and moorland. Progression 

 means more timber ; degeneration means less timber. So long 

 as a wood is progressive the trees are masters of the situation, 

 the canopy is kept close so that the ground-vegetation is kept in 

 check ; in addition, humus is formed and preserved. Degeneration 

 is the reverse of this, and for the signs of it one must look to the 

 ground-vegetation. The injurious effects of a thin canopy have 

 been frequently pointed out in thtse pages, by none more strongly 

 than by Professor Schwappach.^ The ground-vegetation is very 

 dependent on the amount of light. Plants are like photographic 

 plates in this respect that they will indicate differences in light 

 and shade where to the eye there is no appreciable difference. 

 In using the ground-vegetation as a guide, it is necessary to 

 distinguish the growing season of woodland plants. Thus, bracken, 

 which is late in throwing up its leaves, is a good guide ; where 

 it is thick there is a considerable amount of light passing through 



^ Schwappach, A. "The Importance of Density in Silviculture," Trans. 

 Roy. Scot, Arbori. Sor. , vol. xv. p. 3, 1897. 



