REVIEWS 433 



(N). The existing sample plots shall be re-examined, and the results 

 published (S). New sample plots shall be gradually laid out further 

 south (S), with North Swedish pines and, in co-operation with other 

 Scandinavian institutes of experimental forestry, concerning beech, 

 oak, spruce, and alder (S). One or more series of experiments shall 

 be instituted at different heights above sea-level with pine seed col- 

 lected from different adjacent levels (F). The productivity of the 

 seed trees shall be investigated with the object of determining the 

 lowest age in different districts of the country at which such trees 

 can suitably be left (Sj. The total quantity of cones from certain 

 selected trees shall be collected annually, and the quantity and the 

 quality of the seed obtained therefrom shall be investigated (F). 

 Cones shall be collected from old pines and spruces in Norrland, and 

 the quantity and the quality of the seed obtained therefrom shall be 

 investigated (F). 



(b) Special measures for securing natural forest regeneration. 

 Existing experiments with different large clearings and gaps and 

 thinnings shall be controlled and published (S). New experiments by 

 means of thinning in accordance with Wagner's method, or by other 

 methods of cutting shall be arranged when time permits; and in this 

 connection attention shall be paid to the seed-producing capacity and 

 success in regeneration attained by the margins of the stand at dift"erent 

 points of the compass in the areas cleared (S). Areas intended to 

 throw light upon the scattering of the seed, etc., on the tracts cleared 

 in Norrland shall be laid out in four new series with a total area of 

 about i6 hectares (F). Areas intended to compare the value of dif- 

 ferent treatments of the ground soil shall be laid out in Norrland in 

 five new series with a total area of about 12 hectares (F) ; and in ad- 

 dition to this a few series of experiments in ground preparation shall 

 be carried out in old spruce forests that have been thinned. Material 

 shall be steadily collected regarding the effect of measures for refor- 

 estation on the humus covering of the ground (N). 



(c) Silvicultural measures. The experiments instituted for de- 

 termining the most suitable sowing time in Norrland shall be continued 

 (F). Seven new series of plots, intended to compare different methods 

 of sowing, shall be laid out in Norrland with a total area of about 2.3 

 hectares (F). Plots designed for investigating the most suitable age 

 of the clearings for silviculture in Norrland, for which the laying out 

 of two series has begun, shall be augmented by three new series (F). 

 The course of growth in the roots of planted trees shall be investigated 

 with a view to discovering the most suitable times of planting (N). 



