368 ECOLOGY 



Bruce Fink^ found in N.W. Minnesota an association on exposed cal- 

 careous earth as follows : 



Heppia Despreauxii. Biatora {Bacidid) muscorum. 



Urceolaria scruposa, Dermatocarpon hepaticum. 



Biatora {Lecidea) decipiens. 



This particular association occupied the slope of a hill that was washed 

 by lime-impregnated water. It was normally a dry habitat and the lichens 

 were distinguished by small closely adnate thalli. 



There are more lichens confined to limy than to sandy soil. Arnold'' 

 gives a list of those he observed near Munich on the former habitat : 



Cladonia sylvatica f. alpestris. Urceolaria scruposa i. argillacea. 



Cladonia squamosa f. subsquamosa. Verrucai ia ( Thrombium) epigaea. 



Cladonia rangiformis tfoHosa. Lecidea decipiens. 



Cladonia cariosa and f. symphicarpa. Dermatocarpon cinereum. 



Peltigera canina f. soreumatica. Collema granulatum. 



Solorina spongiosa. Collema tenax. 



Heppia virescens. Leptogiwn byssimim. 

 Lecanora crassa. 



It is interesting to note how many of these lichens specialized as to 

 habitat are forms of species that grow in other situations. 



b. On siliceous soil. Lichens are not generally denizens of cultivated 

 soil ; a few settle on clay or on sand-banks. Cladonia fimbriata and CI. 

 pyxidata grow frequently in such situations ; others more or less confined to 

 sandy or gravelly soil are, in the British Isles : 



Baeomyces roseus. Congylia viridis. 



Baeomyces rufus. Dermatocarpon lachneum. 



Baeomyces placophyllus. Dermatocarpon hepaticum. 



Endocarpon spp. Dermatocarpon cinereum. 



These very generally grow in extended societies of one species only. 



In his enumeration of soil-lichens Arnold^ gives 40 species that grow on 

 siliceous soil, as against S7 on calcareous. Many of them occurred on both. 

 Those around Munich on siliceous soil only were : 



Cladonia cocci/era. Baeomyces rufus. 



Cladonia agariciformis. Lecidea geldtinosa. 



Secoliga {Gyalecta) bryophaga. Psorotichia lutophila. 



Mayfield* in his account of the Boulder Clay lichen flora of Suffolk found 

 only four species that attained to full development on banks and hedgerows. 

 These were: Collema pulposum, Cladonia pyxidata, CI furcata v&x. corymbosa 

 and Peltigera polydactyla. 



1 Fink 1902, etc. '^ Arnold 1891. ' Mayfield 1916. 



