The Shingle Beach as a Plant Habitat. 
97 
up the bank also loosened and conveyed the drift to the lee slope, 
where it became imprisoned by the talus of shingle washed over 
the crest. 
Thus it is evident that the same mechanism which builds up 
the bank and keeps the shingle mobile, also provides that which is 
required to give it fertility. 
Nor is this all. Drift is not mere organic matter; it is also 
the great agency by which seeds are brought to the bank—the seeds 
of the plants which establish themselves there—and it is under its 
protection that they germinate. From our point of view the drift, 
therefore, is the all important thing. 
The nature of the drift. The components of the drift are 
recruited from the salt-marshes, and include everything on the 
marsh or mud flats that the tide can sweep up. Alg^e such as 
Rhizoclonium and Enteroniorpha ; the leaves of Atriplex ( Obione) 
portulacoides ; the stalks and chaff of Spartina ; twigs of Suceda 
frnticosa ; the dung of rabbits which browse on the marsh ; the 
carcases of small crabs and other animals which perish ; and above 
all in quantity, the rhizomes and leaves of Zostera. 
Tidal drift provides a field of special study yet to be opened 
up. The manurial value of various drifts has never been systema¬ 
tically investigated. The seasonal phenomena connected with 
drift and the relations of drift to the plant and insect-life of the 
shingle bank, these and other departments of the subject would 
doubtless reward investigation. At present it is only possible to 
state the crude fact that the same machinery which organises the 
spit, provides also the means of its fertility. 
To appreciate the significance of the drift it is only necessary 
to see how those shingle banks fare which are denied contact with 
tidal waters. Apposition banks are of this order and they are 
notorious for their enduring sterility. The same result is apt to 
appear when the salt-marshes under the lee of a shingle spit are 
dyked off and the tidal waters excluded. The drift no longer 
circulates and the bank is starved of its lawful food. Nor can the 
marsh-holders hope indefinitely to continue in the enjoyment of 
the reclaimed land. The starved portions of the shingle spit 
will tend to become more and more sterile and proportionately 
more mobile, and Nemesis will overtake them in the form of exces¬ 
sive encroachment of the shingle on the dyked marshes. 
“ He who will not Nature’s way, 
Will in good time have to pay.” 
