THE BROWN SEAWEEDS OF THE SALT MARSH. 339 
Kolderup-Rosenvinge (1898, р. 218), which is analogous to the “ Migrations- 
formation ” described by Schiller (1909, рр. 62-98) from the Adriatic Sea. 
All the loose-lying formations occur within the sublittoral region. They 
are composed of different forms derived from the attached species of 
the littoral region, which, when torn loose by the waves and carried by 
the currents into still places, collect together in great masses on the floor 
of the sea. Here they continue to grow, reproducing themselves by vege- 
tative means, often over a mobile bottom, otherwise destitute of vegetation ; 
but they never become embedded or fixed to the substratum. 
The dwarf Fuci are dominant forms in the uppermost of the two chief 
loose-lying formations of the Baltic; the formation characteristic of deeper 
waters is dominated by Phyllophora Brodiaei f. elongata. The loose-lying 
Fucus formation occurs, in general, at a little depth, varying from 8-10 
metres ; but occasionally the formation may extend up to the lower limits of 
the littoral zone. 
The Loose-lying Fuci. 
The loose-lying Кий are uniformly sterile, but Svedelius was able to 
collect a number of intermediate forms, which led up to well-established 
and fertile attached varieties of F. vesiculosus. He separates three distinct 
series of loose-lying Fuci, naming them, according to J. G. Agardh's system, 
f. nana, Ё. subecostata, and f. filiformis of Fucus vesiculosus. 
The f. nana series is characterised by folds and curves in the margins of 
the thallus and eryptostomata, which are very indistinct and scattered, or 
else wholly absent. This series leads by intermediates to F. vesiculosus 
у. plicata, Kjellm. Arcichovskij (1905) figures a detached specimen of 
F. vesiculosus (p. 28, fig. 9) in which the old parts had weathered away to 
the midrib and new shoots had arisen at the tip with the habit of the form 
nana but bearing minute male receptacles. 
The f. subecostata series is characterised by prominent cryptostomata 
arranged in two rows, one on either side of the midrib in the larger forms, 
and marginally in the smaller forms. This series leads through intermediates 
to F. vesiculosus f. angustifolia, С. A. Ag. 
The f. filiformis series is characterised primarily by complete absence of 
eryptostomata, many of the larger forms are otherwise identical with the 
subecostata series ; but the smallest forms reach filiform dimensions. These 
forms again lead up to F. vesiculosus v, angustifolia. 
Areichovskij (1905, p. 136) has further subdivided these three series, but 
as his distinctions depend mainly upon the system of branching, which is 
always highly variable in the dwarf Fuci, they seem to rank rather as sub- 
divisions of these groups than as distinct forms. 
It will be seen that we have here a complicated series of forms which are 
in many ways parallel to the small Fuci of our salt marshes and derived from 
the same species, F. vesiculosus, but which are undoubtedly not identical with 
