BROWN SEAWEEDS OF THE SALT MARSH. 283 
The effect of this matting of Pelvetia on the growth of Salicornia europea 
is shown to be decidedly favourable. How this effect is produced is not 
so clear. It is not easy to see how an entirely unattached living layer of 
plants could become an efficient manure. Also when the embedded Fucus, 
which rots below and thus affords manure, grows with Salicornia there is 
rather a dwarfing of the Salicornia than otherwise. Тһе cause is probably 
to be sought in the decreased evaporation from the surface of the soil, and 
slightly increased temperature, produced by the Pelvetia, which acts as a 
surface mulch. It is hoped that further experiments may throw some light 
on this subject. 
Zoning between the Free Pelvetia and the Fucus.—In the lower parts of the 
marsh, аз Salicornia is replaced by Aster Tripolium, the place of Pelvetia is 
taken by a small spiral Fucus. Between the entirely loose Pelvetia and the 
embedded Fucus there is quite a comparatively detinite zoning observable, 
which is all the more interesting as the differences in level involved are very 
small, a few inches at most. The spring-tides apparently only covered the 
Aster zone 10 to 15 minutes earlier than the Salicornia zone. The number 
of tides covering the areas is probably the determining factor, not the 
exposure per diem. 
THE EMBEDDED Fucus. 
The small spiral Fucus found in the lower regions of the marsh, among 
the Aster association chiefly, is not by any means a new form. Among 
others, Hudson *, Goodenough & Woodward, and Turner + have described it 
in England ; and a closely similar species, occurring at Arcachon in France, 
has been deseribed and discussed very fully by Prof. C. Sauvageau under the 
name of F. lutarius ў, a species established by Kützing $. 
The general morphology of our plant is almost identical with the И. lutarius 
of Sauvageau, with specimens of which he has most kindly supplied me. 
The thallus is extremely spirally twisted, and bears eryptostomata on the 
margins at frequent intervals, and often scattered over the rest of the thallus. 
A comparison of PI. 8. fig. 3 and Pl. 9. fig. 4 and text-figs. 5,16, 7, & 8 with 
figs. 16-19 of Sauvageau's paper (loc. cit.) will show the great similarity of 
the two forms. 
Mode of Growth and Occurrence of the English Fucus.—The plant found at 
Blakeney (text-fig. 5, A) varied in length from 5-12 em. It was much 
spirally twisted and grew embedded in the soil, numerous adventitious shoots 
* í Flora Anglica, р. 577. London, 1778. 
T ‘A Synopsis of the British Fuci, vol. i. p. 127. London, 1802. 
{ Bordeaux Société Scientifique d'Arcachon, Travaux des Laboratoires, 1908, pp. 106-153. 
$ Kützing, Tabule Phycologice, vol. x. p. 7 & pl. xvii. Nordhausen, 1860. 
