70 
Litteraturförteckning. 
Hesselman: »Studier over salpeterbildningen i naturliga jordmäner», 
Medd. fran Statens Skogsförsöksanstalt 1916 — 1918. 
Lunge et Berl. : Chem.-teckn. Unters. -meth. II. 1910. 
Sernander: »Förna och ävja». Geolog. Föreningens Förhandlingar 
1918. 
Skottsberg: »Om växtligheten à nâgra tängbäddar i Nyländska skär- 
gârden i Finland». Sv. Bot. Tidskrift 1907. 
Warming: Dansk Plantevæxt, 1906. 
— , Lehrbuch der ekologischen Pflanzengeografphie. 
Weibull: »Biologiskt-botaniska undersökningar av Öresund I». Kungl. 
Fysiograf. Sällskapets handl. Bd BO, nr 7. 1908. 
Summary. 
1. Fucoid mud (Swedish: »ävja») is a jmtrescent 
mass in which Zostera-leaves and algæ cast up out of 
the sea, mainly Fucus-species, are discernible. 
2. The vegetation presents a decided zonal struc- 
ture. A marked feature is the variety of biological 
types, special attention being called to the halophytes 
and bog-plants, of which the former dominate in the 
lower parts, the latter in the upper parts of the »ävja». 
Close to the sea there is no vegetation. Analysis of 
the vegetable growth was done by means of the quadri- 
metric method. 
3. Among the ecological factors special attention 
was paid to the percentage of water, nitrate and salt, 
and to the acidity and percentage of H 2 S. The percentage 
of water amounts to about 80 % . The percentage of salt 
and the acidity decrease from the shore upwards; the 
former is always below 1 ^ (sea-water about 1,5 
Maximum of acidity in vegetation-clad parts was reckoned 
at 0,oi8 n. a constituent part of w T hich is caused by H 2 S. 
An estimation of the concentration of the liydro- 
gen-ions by means of the indicator method gave re- 
markable low values. The decisive ecological factors 
obviously are the acidity and the percentage of salt. 
