Physiologie. — Algäe. 243 



nur in Verbindung mit anderen Faktoren eine wesentliche Kei- 

 mungsverzögerung bewirkt. Matouschek (Wien). 



Baker, S. M. and M. H. Bohling [afterwards Blandford]. 



On the Brown Seaweeds of the Salt Marsh. — Part II. 

 Their Systematic Relationships, Morphology, and 

 Ecology. (Journ. Linn. Soc. Bot. XLIII. p. 325—380. 3 pl. and 18 

 text figs. November 1916.) 



The authors made a special study of the peculiar forms of Fu- 

 caceae which occur conspicuously on some salt marshes, and their 

 relation to recognised species, and also of the effect of the physical 

 conditions of the marsh upon the morphology of the plants. The 

 marsh forms are traced to five, out of our seven littoral Fucaceae, 

 viz., to Pelvetia canaliculata, Fucus spiralis, Ascophyllum nodosutn, 

 Fucus vesiculosus, F. ceranoides. The ecological forms of the salt- 

 marsh have hitherto been neglected or misunderstood. Though 

 differing widely from their rock ancestors, they are to be regarded 

 as adaptational varieties or ecads, Fucus vesiculosus has yielded a 

 long series of ecads of confused nomenclature, commonly appearing 

 under the names F. volubilis Huds., F. lutarius Kütz., F. balticus 

 Ag., F. subcostatus Ag., or as varieties of F. vesiculosus (var. muscoi- 

 des Cott. and var. spiralis Farl.). These forms are parallel to but not 

 identical with the series of forms of F. vesiculosus found in loose- 

 lying associations of tbe Baltic, as described by Svedelius and Ar- 

 chichovsky. The salt-marsh ecads from each species are grouped 

 by the authors under one megecad limicola, whose chief character- 

 istics — viz. Dwarf habit, Vegetative reproduction, Spirality, or 

 Curling, Absence of attachment disc — are common to the marsh 

 forms of all the species. Under the megecad limicola of Pelvetia 

 canaliculata are three ecads — e. radicans (Fosl.), e. coralloides 

 (S. M. Baker), e. libera (S. M. Baker). The marsh form of F. spira- 

 lis is var. nana Kjellm., with normal reproduction. Ascophyllum 

 nodosum has var. minor Turn, and under megecad limicola has e. 

 scorpioides (Hauck) and e. Mackaii (Turn). Under the megecad limi- 

 cola of Fucus vesiculosus is a Marsh section, with cryptostomata 

 marginal — e. volubilis (Turn.), e. caespitosus, e. muscoides (Cotton); 

 and a Loose-lying section, with cryptostomata variable — e. nanus 

 (Ag.), e. subecostatus (Ag.), e. filiformis (Ag.). There is also a new 

 megecad limicola derived from F. ceranoides. 



As to morphology, two general methods have been employed to 

 study the correlation between the peculiarities of the marsh forms 

 and the new chemical and physical conditions of their environment. 

 The first is to study the distribution of natural varieties of one 

 species, and the second to examine in detail exceptional cases. 

 These methods have led to the conclusions that dwarf habit is 

 mainly due to exposure and to lack of nutrient salts. Vegetative 

 reproduction is caused by the high humidity maintained over the 

 marsh in the intertidal periods. This prevents the attainment of a 

 limiting concentration in the cell-sap necessary as a Stimulus to the 

 formation of sexual reproductive organs. The cause of spirality is 

 probably an unequal distribution of nutrient salts. The same fac- 

 tors are also shown to be operative in causing the change in mor- 

 phology of the floating Sargasso weed. 



As to ecology, the brown seaweeds on salt-marshes may serve 

 either as pioneer Vegetation, or as undergrowth, or for covering 



