5o8 SCIENCE PROGRESS 



than on fertile soil. On poor land from which the foliage is 

 taken annually, Beech-woods will become so open and backward 

 in growth, and the soil will become so top-hardened and over- 

 grown with unfavourable weeds, as to make natural regenera- 

 tion impossible; while on better soil natural regeneration is 

 made much more difficult, and less likely to be satisfactory 

 as regards the young crop raised. The direct effect of the 

 removal of dead foliage is less apparent in Pine or Spruce 

 woods on good soil, but on poor soil it soon shows its effect 

 in a very considerably diminished rate of growth. Its indirect 

 effect is even greater, however, when such tracts are cleared 

 and replanted ; and the absence of humus altogether, as on 

 old fields or pastures and poor waste lands, is even more 

 marked ; for, though the foliage of young four-year-old crops 

 of Scots Pine only need from 3 to 8 kilos, of lime, potash, and 

 phosphoric acid for the production of their foliage, yet they 

 wilt through want of the nitrogen that can be supplied by 

 humus. Such sickly plantations are then likely to be attacked 

 by insects and fungoid diseases. On the other hand, of course, 

 any mossy or peaty raw humus must hinder natural regenera- 

 tion wherever it is so thick as to prevent the roots of seedlings 

 from getting down into a layer that can supply it with the 

 necessary plant-food ; while an}' deep layer of such raw humus 

 has an unfavourable physical influence on the development of 

 the plants, even though the necessary substances for providing 

 plant-food may be abundantly contained in such a soil — though 

 not in a form making them available for imbibition by the root- 

 system. That peaty raw humus can even, under changed 

 conditions as to the soil, become of considerable manurial 

 value has been shown by the successful results obtained in 

 Prussia through manuring sandy nurseries for Scots Pine 

 with peat. 



The best method of ensuring a humus favourable to soil- 

 productivity is to grow timber-crops in mixed woods consisting 

 of kinds of trees suitable to the soil and situation, and capable 

 of protecting the soil against the deteriorating effects of sun 

 and wind ; and in such mixed woods the Beech has on the 

 Continent been found to possess the most valuable properties 

 regarding the conservation and the increase of soil-productivity. 

 Towards this end, too, caution should be exercised in making 

 thinnings ; and when light-demanding crops, like Oak, Larch, or 



