and the sand around the roots of Hippophaes. The N03 concentration of the soil liquid in the first case was 7 times the nitrogen content in the latter (0.1-0.3 NO3 per 100 gr of dry sand for Ammophila). The suggestion was put forward that this might have connection with a different way of N-supply: Ammophila autotrophic, Hippophaes heterotrophic.

An exception in the lixiviated area was found in the erosionkettles, where as a consequence of the deposits of whirled-out nutritive sand from the centre of the kettle, the vegetation rejuvenates and Ammophila develops again. A definite contrast came to light between the sand from the centre and the whirled-out sand of the stowzone on the outer slopes at the east-sides of the kettles (210-240 mg NO3 per liter of soil'liquid), and, on the other hand, the sand from the arid, outer slopes at the south-sides of the kettles which was without any nitrogen.

In conclusion the three different sources of N-supply are compared:

1) the amount transported with the dried sands from the high-water lines enriched with N-containing material of cadavers and blown to the habitats of Ammophila (1 mg NO3 per 100 gr of dry sand) ;

2) the amount carried in our country by the rain water during one year (2 mg NO3 per dm2, corresponding with the equivalent quantity NO3 in a layer of 0.8 cm of the sub. 1) mentioned sands from high-water lines) ;

3) the maximum amount present in the wet sands of the beach saturated with sea water of the highest N-degree (0.04 mg NO3 per 100 gr of dry sand).

1 hese data show that the sands blown inland from the high-water lines are the main source of nitrogen for the vegetation of the outer dunes.

GECITEERDE LITERATUUR

Boer, S. de, Nitrate assimilation of Aspergillus niger van Tieghem. (Proc.

Kon. Akad. Wetensch. Amsterdam. 43 (1940), pag. 715-720).

Bruce, R., Physical factors on the sandy beach. (Journ. mar. biol. assoc. 15

(1928), pag. 535-551 en 553*565).

Dieren, J. W. van, Organogene Dünenbildung. Proefsch'r,. Amsterdam, 1934. Harvey, H. W., Nitrate in the sea. (Journ. mar. biol. assoc., 14 (1926-27)

pag. 71-88 en 15 (1928), pag. 183-190).

Heukels, H., De flora van Nederland. 1921, deel I, pag. 60.

Leeflang, K. W. H., De chemische samenstelling van den neerslag in Nederland. (Chem. weekbl. 35 (1938), pag. 658-664).

Schucht, F., Über die Beziehungen zwischen Boden, Vegetation und Klima auf den ostfriesischen Insein. (Intern. Mitt. Bodenk. II (1912), pag. 485-532). Wicke, W., Über die Bodenarten der Insel Borkum und ih're Benützung. (Journal für Landwirtfchaft, Neue Folge 8 (1863), pag. 99-116).