34. EXPLOITATION OF PLANTS 
is Mr. P. E. Martineau. His principal criticism of the 
earlier plantings is that they would have been better 
with the trees at four feet instead of five feet intervals 
(i. e. 2722 in place of 1742 per acre), especially on wind- 
swept areas. Future developments will doubtless con- 
form to experience in this matter. It is to be hoped 
and expected that other coalfields may follow the lead 
of the Midlands Association in the period of recon- 
struction after the war. 
MariTIMeE WASTES 
By the sea shore products of erosion accumulate in 
the form of sand dunes, shingle beaches and salt 
marshes, terrains the possibilities of which have been 
_ too long neglected in this country. 
1. Sand dunes—These attain their fullest develop- 
ment in Gascony, along the Bay of Biscay, in North 
Holland, and in Baltic Prussia. Owing to their extent 
and to their great capacity to ‘‘ wander ’’ before the 
prevalent winds, the dunes of these regions have been 
very fully studied for more than a century, and the 
technique of their fixation by means of vegetation has 
reached a high degree of perfection. They are fixed 
partly by planting Psamma (marram grass), partly by 
afforestation, especially with coniferous trees. In 
Gascony productive forests of Pinus Pinaster have arisen, 
whilst on the Baltic a variety of coniferous and broad- 
leaved trees are employed. In Gascony the pinasters 
are exploited for their turpentine, and when they have 
run dry they are felled to provide pit timber, largely for 
the South Wales Coalfield. 
