240 



PLANT SOCIOLOGY 



In the mountains of central Europe the tall-herb association of the 

 Adenostylion, which inhabits well-aerated, moist, weakly acid to basic 

 soils, seems to be determined by the high nitrate content of the soil 

 (Fig. 70). Nitrophilous communities are very widely distributed in 

 dry, subtropical regions (Fig. 119). The most nitrophilous community 



Fig. 119. 



-Nitrophilous association with Magydaris torncnto>ia near Meknes, Morocco. 

 (Photo by Maire.) 



of the Mediterranean region is the Silyhum-U rtica pilulifera association 

 of which all the species show a high nitrogen content when young. 



Notable among nitrophilous communities are the lichen associations 

 (examined by Sernander (1912), Frey (1922), Gams (1924), Motyka 

 (1924), etc.) of bird roosts and marmot rests, of stones and rocks wet 

 with goat and sheep urine, and of similar, overmanured places. 



If the supply of excreta is too great, only a few species can thrive, 

 and even these are frequently dwarfed. According to their degree of 

 nitrophily, the rock-lichen communities are often arranged in distinct 



