PLANTING OF SAND DUNES. 79 



tion of sand has been known to form monnds 100^ meters high, burying 

 hills of half this height, and trees that grew upon their summit.^ 



When this protecting dune has been well established the task of 

 planting the sands under its shelter is begun, and continued until all 

 the sands in the rear, perhaps a dozen miles wide, are brought under 

 forest cultivation. From the extremely light and arid nature of the 

 sand, it would be impossible to transplant trees,^ and the only chance of 

 success depends upon the possibility of seeding and protecting the 

 young plants until they can take care of themselves. The surface is 

 accordingly sown broadcast with a mixture of seeds of the maritime 

 pine {Pinus pinaster), the common broom {Sarotkamus scopariiis), furze 

 ( Ulex nanus), and beach grass {Psamma arenaria). Where the planting 

 is done by the forest administration, the quantity of seed used is 10 kilo- 

 grams of the pine, 9 of the broom, 4 of the Psamma.* The surface, 

 after sowing, is spread over with a covering of broom, furze, and other 

 brushwood, which is brought in bundles and, when spread, is held down 

 by a spadefull of earth thrown on at intervals of about twenty inches. 

 This covering is essential for preventing the seeds from being blown 

 away by the wind, and some fertility is given to the soil by its decay. 

 The sowing of the seed and spreading of the brushwood must be done 

 at the same time, and the last row of the covering at the end of a day's 

 work, must be secured by an additional load of earth, to prevent the 

 wind from getting under and scattering, perhaps, the work of several 

 days. 



The pines, furze, and broom sprout and come up together, and the ten- 

 der shoots of the pine grow best when well screened by the other plants. 

 The protection of the brush-wood must be kept in place about four years, 

 and its maintenance constitutes the principal operatiou during this pe- 

 riod. 



The littoral dune may in some cases be itself seeded with pine, a new 

 dune being formed still nearer to the sea. But in any event a shelter- 

 ing dune is indispensable, and its maintenance becomes a permanent 

 object of expense. It will be readily seen that this undertaking is diffi- 

 cult, and that the direct profit consists in the general benefit to the 

 country protected, and the damages from encroaching sands that are 

 prevented, rather than in the value of the lands actually redeemed. The 

 cost is sometimes as much as $40 per acre, as labor is paid in France, 

 But in securing this result incidental advantages are secured beyond the 

 immediate area of the sands stocked with piues. The shallow lagoons 

 and marshes behind the sands gradually become dry, and cultivation be- 

 comes possible over wide areas as these become more and more sheltered 

 by the growing forest. Finally, the timber of the plantation becomes a 

 source of profit from its affording resin through a series of years, and 

 then wood ; but these are always to be considered as subordinate results, 

 which are not to be sought at the sacrifice of the main object for which 

 the plantation was made.^ 



1 Equal to 3'27 feet. Laval, cited in an article upon littoral dunes in the Revue dea 

 Eaux et Forets, 1875, p. 131. 



2 In the Gironde and La Chareute Infdrieure the dunes extend 12J miles inland and 

 are in some places 200 meters high. 



3 As soon as the radicle is developed it begins to strike into the sand for moisture, 

 and it sometimes grows a foo^ or more in length while the plant above ground is gain- 

 ing an inch. The capillary attraction of the sand is often quite remarkable, and moist- 

 ure will be found a little ways down where the surface is as arid a9.pos8ible. 



••Equal to 9.4 pounds of pine, 8.36 of broom, and 3.76 of Psamma to the acre. 



6 The forest administration in France has fixed the price at 30 francs per hectare 

 ^$2.40 per acre) as the normal revenue of the dunes when planted and brought to full 

 capacity of production. The whole extent of dnnes in France that remained to be 



