THE STRUCTURAL CHARACTERISTTCS OF TTfE COMMTIXITY 45 



In the Juncus acutiflorus fiat moor of the mountains of central 

 France the tall (2 m.) composite Ligularia sihirica develops to its full 

 capacity. Thanks to its eflaciency in seed production and dispersal, 

 seedlings of Ligularia are also distributed all over the immediately 

 adjacent Trichophoretum. Very few, however, attain therein to a 



Fig. 25. — Root layering in the Mediterranean red-earth soil near Montpellier, 

 France. A, Che«tnut-brown horizon with roots of therophytes and geophytes, Brachy- 

 podium ramoaum dominant; B, reddish brown horizon with roots of nanophanerophytes, 

 Quercus coccifera, Rhamnus alaternus, and Asjjaragus acutifolius; C, horizon of rock 

 fragments with roots of Quercus ilex in crevices. {Photo by Braun-Blanquet and Keller.) 



leafy stem, and none flowers, the young plants perishing very quickly. 

 The vitality of Ligularia is evidently greatly reduced in the 

 Trichophoretum. 



Profound changes in vitality in the undergrowth follow admission of 

 light or clearing of timber. Shrubs like Vaccinium myrtillus, Calluna, 



