THE STRUCTURAL CHARACTERISTICS OF THE COMMUNITY 51 



summer-green type determines the aestival aspect. The hne of divi- 

 sion between vernal and aestival aspects is given by the leafing out of 

 the trees and shrubs. The vernal leafless "light phase" enjoys a light 

 intensity in the undergrowth of 40 to 60 per cent. After leafing out 

 the light intensity often falls in the aestival aspect to 1 per cent or less 

 of the light requirement (Lichtgenuss) . 



The periodicity of the Mediterranean garigue is caused not by light 

 relations but by the spring and autumn rains. To the four 

 seasonal types mentioned above there is here added a fifth, the autum- 

 nal, with Thrincia tuberosa, Bellis silvestris, Scilla autumnalis, etc., 

 corresponding to the reawakening of growth after the first autumn 

 rains (Fig. 31). 



Instead of the period of photosynthesis, the preceding diagram 

 (Fig. 31) gives the seasonal variation in volume of each species. In 

 this the summer drought comes out strongly with corresponding 

 minimum of plant volume. On the whole, however, the Quercus cocci- 

 fera garigue is "periodically saturated"; that is, it includes species 

 which substitute for one another throughout all seasons. 



