.•1ii4 JOIIS. IJOYi; l'KTKHSKN 



aiiliimn(ili\ which lonned i)relly, silky, alinosl l)l;uU Invers. It is 

 a chiirncleristic faet lliat lliough tlie grouiui was lairly moist, no 

 Dialoms were found liere. Presumahly lliey have nol been ahle lo 

 stand the streng nianure. 



1). Soil Sdturateil wilh Vrine. (Samples 172, 173). 



Al Ihe larm I U'sbær in X. leeland was a lank willi li(|ui(i ma- 

 nure round \vliieh the ground was f[uite saturated wilh urine. Here 

 was likewise found an abundant vegetation of Phormidinm (lutiimuale. 

 Mixed wilh it were small patehes of Prasiola crispa whieh did nol 

 seem lo Ihrive very well where there was jilenty of urine, it was 

 only al some distance from the tank thai Prasiola formed vigorous 

 growths. Il is a characteristic faet thai no Dialoms were found 

 among the Phormidium, whereas there were manj' of them, though 

 only few species (S in all), among the Prasiola. Presumahly the 

 Diatoms cannot live in the mucilaginous sheaths of Phormidinm 

 auliimnale, while they evidenlly thrive well among the lilaments or 

 leaves of Prasiola crispa. The species most commonly occurring 

 was Xaniciihi nitrophila. 



c. Hla') (14, 78, 92, 114, 121, 131, 161, 162, 242, 252, 282, 295, 298, 307, 



327, 372). 



»HlaO« in Iceland means a strelch of ground in front of the 

 house where there is a conslanl traflic of people and animals and 

 where, consecjuentiy, piants can only Ihrive (juite close to the house, 

 and where the »hla(V< abuls on the »tiin« or homelield, (Jonsson 

 1900, p. 58). I shall here include under Ihe hlai^ the Irampled areas 

 at the sides and back of Ihe house as well as a sample from a 

 sheep-fold where similar conditions and a similar vegetation are 

 found. The iilaO is always fiiirly well manured, hence Ihe vegeta- 

 tion has a nilroi)hilous character, 'l'he predominaiit alga here is 

 Prasiola crispa found in 14 of the 16 samples, of rarer oicurrence are 

 Phormidium autnmmde (2 samples) and Vaiicheria hamata (I sample). 

 Diatoms always occur wilh Ihese, often in a great number of species 

 and individuals. The characteristic species are Nanicnla niirophila. 

 and N. Atomiis. Haidzschia amphioxijs , Nanicnla mnlica f. Cohnii, 

 Dialomella Firdfonriana, Pinnnlaria borealis, and P. parua n. minnta 

 are also common P. horealis occurs in nearly all Ihe samples, but 

 onlv in a small numbt r of individuals. 



