250 Studies in Forestry [CHAP. xi. 



induces stag-headedness among the standards, owing to in- 

 sufficiency of moisture in the layer through which the roots 

 ramify, and from which they extract their food-supplies. This 

 may, however, not infrequently be due to injudicious thinning or 

 partial clearance on soils that are below the average in quality 

 and are naturally rather deficient in moisture though the evil 

 is then, of course, aggravated by the selection of Spruce as 

 underwood. 



Although endowed with considerably greater capacity for 

 bearing shade than Scots Pine, the Weymouth and Black Pines 

 are not naturally adaptable for undergrowth ; far better results 

 are promised in this direction by Nordmann's Fir and perhaps 

 also by the Douglas Fir, which in many respects correspond 

 closely with the Silver Fir. 



Although the richest fall of dead foliage takes place when 

 the whole of the standard crop is underplanted, yet the 

 advantages of partial underplanting, with reference to decreased 

 competition with the standards for the nutrient salts held in 

 solution by the soil-moisture (for it is only when soluble that 

 they can be imbibed by the rootlets), are so apparent as to 

 make this method preferable on soils of only average or inferior 

 quality. Because, whilst extracting smaller supplies of nutriment 

 from the soil, it permits of a larger percentage of the aqueous 

 precipitations reaching the soil, and of a somewhat speedier 

 decomposition of the dead foliage than under close canopy, 

 without endangering the quality of the soil through insolation 

 and wind. That, by arranging the underwood in patches, better 

 opportunities are given for studying the special character of 

 each particular piece of ground, and for selecting the shade- 

 bearing species best suited for it, with the additional advantage 

 of attaining a mixed growth of underwood, need hardly be 

 commented on ; nor the fact that, for the formation of under- 

 growth in patches, only a much smaller outlay will usually be 

 requisite than if the whole area be planted up or sown. 



Whether the underwood should be formed by sowing or 



