374 DR. SARAH M. BAKER AND MISS M. H. BOHLING ON 
Distribution of Marsh Fucoids in relation to the Salinity of the Water. 
In cases of extreme dilution of the tidal waters, we get on the marsh, as 
on the seashore, a replacement of marsh Fucus vesiculosus and Ascophyllum by 
the marsh Fucus ceranoides. This is shown at Keyhaven. The only com- 
ment which is necessary in this connection is that, because of the retention of 
salts by the flat soil, the marsh Fueus-ceranoides does not appear at such a 
high concentration of water as its rock analogue, so that the other marsh 
alge hold their own up to a much greater dilution than they could under 
normal shore conditions. 
Epiphytes and Undergrowth subsidiary to the Fucoid Undergrowth. 
The undergrowth of brown alg: is not generally by any means a pure 
formation. Very frequently it is accompanied by a ground flora. The per- 
sistence of this ground flora is a measure of the density of the algal matrix, 
and it is a noteworthy fact, that under Pelvetia canaliculata ecad libera 
the ground flora is completely absent. The usual species represented are 
those which normally comprise the undergrowth of salt marshes :— Catanella 
Opuntia is very common and also a small peculiarly curled variety of Entero- 
morpha intestinalis, which grows loose among the Fucus in the Blackwater 
marshes. Besides these the filamentous green alge, and especially Rhizo- 
clonium riparium, persist asa covering to the marsh and under the brown alge. 
The epiphytic vegetation is often quite luxuriant. It is interesting to 
find that Ascophyllum retains its epiphytic Polysiphonia fastigiata on the 
salt marsh. Also that Polysiphonia violacea, various Chatomorpha species, 
Catanella Opuntia, Rhizoclonium riparium, and the characteristic salt-marsh 
alga, Bostrychia scorpioides, are all frequent as epiphytes, especially with 
Fucus and Ascophyllum. 
Other epiphytes, encouraged no doubt by the humid conditions of the marsh, 
are very common—various species of Æctocarpus, Oncobrysa adriatica, and 
other small gelatinous algæ frequently enveloping the fronds of the thallus. 
These are found on Pelretia as well as upon Fucus and Ascophyllum. 
We have not werked out this epiphytic and undergrowth vegetation in 
detail, but the general report on the Marine Algæ of Blakeney Point, now 
in course of preparation by Mr. A. D. Cotton, will contain specific infor- 
mation regarding that area. 
The Fuci are not without endophytes: fungal hyphæ are often to be seen 
in microscopic preparations, especially of the marsh Pelvetia; Mycospherella 
Pelvetie, Suth., is apparently constantly present (see Sutherland, in the 
‘New Phytologist,’ xiv. (1915), p. 34), and other species are frequent, as the 
same author as shown in subsequent papers. 
Besides this, the dense undergrowth of alge, especially the Pelvetia at 
Blakeney Point, forms excellent cover for innumerable small erabs, shell- 
fish, and other animals. 
