WASTE LANDS 39 
the vegetation phases on the mud flats before the pro- 
posed intake is sufficiently advanced for banking. On 
mud flats, as elsewhere, the vegetation shows “ succes- 
sions ’” which are subject to delays, owing sometimes to 
lack of seed of the plants of the next phase, sometimes 
to mobility of ground or other cause. By close study 
of these successions it is easy to recognise when a given 
phase is overdue, and its appearance could doubtless be 
accelerated by sowing seeds or by treating the ground 
in some appropriate way. 
On the other hand, we deepen navigable rivers by 
dredging, and the sludge is commonly taken out to sea 
in barges and dumped. Thus at the mouth of the 
Thames we dispose in this way of enough mud in a single 
year to raise the level of 1000 acres of the low-lying 
shore by as much as three feet. On the tidal reaches 
of the Seine such materials are carried over the banks 
and used to level up low marshy ground, rendering it 
suitable for agriculture and tillage. Is there any reason 
for this divergence in procedure ¢ 
UTILISATION OF NATURAL PRopUCTS OF SALT MarsHEs 
Before leaving the subject of the salt marsh, there 
is the possibility of direct utilisation in contradistinc- 
tion to reclamation. The species of plants that flourish 
on tidal marshes are, as is well known, limited in 
number; not more than 1} per cent. of all British 
plants are halophytes, and this, of course, circumscribes 
the possibilities of utilisation. _ 4 
There is, however, on the South Coast a plant which 
