1903] VEGETATION OF THE BAY OF FUNDY MARSHES 367 
then above it comes often a band of the Hordeum, above which 
comes the couch, later to be noticed. 
The true ecological relationships of the several forms to one 
another, to what extent they are brought together simply by 
coincident habitat, to what extent they are of mutual benefit or 
disadvantage, to what extent some profit by the presence of 
others and those others are indifferent to them, to what extent 
and by what method they compete with one another, is unknown, 
and must be determined by the studies of the future. Such 
hints as we have upon these matters are little better than guesses, 
and such they will remain until thorough experimental study shall 
give the answer to these most difficult problems. 
Theinterrelations of the three associations within the salt marsh 
formation have been sufficiently indicated in the preceding 
pages. In summary, the Spartinetum is the association of the 
extreme position where higher plant life is possible; the Salicor- 
netum is the temporary association of new marsh ; the Staticetum 
is the permanent association of the salt marsh in its highest 
natural state of development. On old marsh, the Spartinetum 
and Staticetum come together, obliterating the Salicornetum. 
The adaptations determining this distribution are known to us 
in a general way, but in details hardly at all. 
(To be concluded.) 
