150 



too expensive, one must try to bind tlie movable sand hills by some natural 

 method. Sand grasses are here most valuable, since, by the rapid root de- 

 velopment of the nodes of the buried stolens, they constantly advance over 

 the upper surface and bind it together. Arundo arenaria, L. and Elymus 

 arenarius L. are most frequently used. Besides these, Arundo baltica 

 Schrad, and Carex arenaria L. should be recommended, and, with sufficient 

 moisture, even our quack grasses as well. Among the dicotyledons, Hip- 

 pophac rhamnoides, L. is ver>^ good. Depending upon the admixtures in sandy 

 soil, experiments may be attempted with Salix arenaria L., Lycium bar- 

 barum, L., Ulex europaeus L. and the lime-loving Genista species. 



No matter whether w-e are concerned with sandy soil in the interior, 

 as in the Mark Brandenburg, Oldenburg and Hanover, or with the sand of 

 dunes, the first planting must always take place with the idea of binding the 

 sand with low, rapid growing vegetation. Where nature, in the course of 

 years, has spread out a thin vegetative covering, this should be protected by 

 every possible means, since, in it, we have a basis which cannot be valued 

 highly enough for the ultimate aim of all cultural endeavors, viz., to obtain 

 a protective forest. Even if the vegetation is ever so thin, it still restrains 

 the sand and makes the planting with young conifers possible. With their 

 deeply growing roots they are better satisfied with poor nutritive conditions. 

 In the beginning attention should be paid to the production of a bushy 

 growth and only later extended inland to the cultivation of tree forms. At 

 the sea shore, on all woody plants, a great many branches will always be 

 found which have been killed back by the action of the wind. The most 

 important cultural method is to leave these dead branches on the plants. 

 They break the force of the sea wind and form a natural protection, keeping 

 the foliage alive. 



LowERiNt; OF THE Ground \\'ater Level. 



The building of canals and the regulation of rivers tend to lower the 

 water level in sandy soils and act most disasterously on plant growth. In 

 contrast to the "soil moisture" of the upper masses, the ground water 

 trickles down in the depths, collecting on the impervious soil layers and 

 forming the reserve supply for roots in times of continued drought. 



In regions like the Alpine provinces and the Bavarian plateau, which 

 have a high absolute amount of precipitation and smaller evaporation, the 

 fluctuations of the ground water level controlled by the annual precipitation 

 are of scant significance for vegetation. In regions, however, with scanty 

 absolute amounts of precipitation, and great evaporation, where the annual 

 fluctuations of the ground water level depend on the amount of evaporation, 

 as, for example, on the flat lands of Northern Germany, and where the reg- 

 ular slope of the ground water curve indicates a gradual flowing away 

 through springs and rivers (see Ramann loc. cit. 275) a lowering of the 

 water level by canals and rivers will have tlie most serious influence. The 

 soil dries out very greatly towards the autumn and vegetation becomes de- 



