12 3 4 



Time in hours 



2 3 4 5 



Time in hours 



Fig. 211 A, water loss from samples of Enteromorpha and Chryso- 

 phyceae belts when exposed in their original position on the cUff 

 face. B, water loss during drainage in nature from different levels 

 in the Enteromorpha and Chrysophyceae belts during successive 

 hours in winter. Ej-Eg, Cj-Cg = successive levels. Water loss in A 

 and B expressed as % of that originally present. (After Anand.) 



simple but ingenious method of weighing portions of the mat cut 

 out so that they fitted into waterproof paper dishes which could be 

 put back into position on the shore. The reduced loss from the 

 Chrysophyceae belt as compared with the Enteromorpha is due to 

 the gelatinous nature of the former. This result was obtained de- 

 spite the fact that the evaporating power of the air opposite the 

 latter belt is 1-41 as compared with i-i opposite the Enteromorpha 

 belt, the evaporating power of the Fucus belt being taken as unity. 



B. Physical factors 



(a) Substrate 



The nature of the substrate, whether solid rock, boulders, 

 pebbles, sand, mud or peat, is of fundamental importance in con- 

 nexion with anchorage, the general aspect of the flora being deter- 

 mined to a large extent by this factor. It is essentially a presence or 

 absence factor. On rocky coasts the angle of slope and the presence 



391 



