CHAP. XL] Effects of U nderplcinting 249 



deserve the preference if the protection and improvement of 

 the soil is the main object in view ; whilst Spruce and Silver 

 Fir recommend themselves where it is desired to obtain fairly 

 marketable timber from the underwood as well as from the 

 standards. An underwood of Beech is productive of the greatest 

 improvement in the soil, owing to the rich fall of its dense 

 foliage and the fine quality of the humus formed therefrom. 

 But, owing to the demands it makes on potash and phosphoric 

 acid, it cannot be grown on the poorer classes of soil (just 

 where it is most wanted) ; and in damp localities under Oak it 

 is more apt than Hornbeam to suffer from late frosts in spring, 

 owing to its flushing into leaf about a fortnight sooner than 

 the standards. Where it is only advisable to underplant with 

 Spruce or Silver Fir, or where these may be admixed with 

 Beech or Hornbeam to form undergrowth, the Silver Fir 

 generally deserves the preference, even although its roots strike 

 deeper and its demands on mineral strength in the soil are 

 greater ; for it has on the whole a greater capacity for bearing 

 shade, forms better humus, and is not so apt to close the soil 

 to aeration and atmospheric precipitations, or to hinder the 

 percolation of water from the surface downwards to the sub- 

 soil. And, besides this, it has greater recuperative power later 

 on when the canopy over head becomes interrupted from 

 casual clearances of diseased or sickly stems among the 

 standards. 



For the underplanting of Oak, Spruce is not to be recom- 

 mended, as it tends later on to interfere with the formation of 

 the crown. Beech, or on moister situations Hornbeam, should 

 form the major portion of the underwood, with Silver Fir 

 scattered in patches here and there wherever there is any 

 likelihood of its being allowed to develop into marketable 

 dimensions. Most of the eminent sylviculturists in Germany 

 condemn the use of Spruce as undergrowth to Oak, and urge, as 

 chief of the several reasons, that, by intercepting and utilizing 

 a considerable percentage of the atmospheric precipitations, it 



