30 
the diminution of available nitrates and phosphates in 
sea-water which, as Atkins, Harvey and others (Publica- 
tions from the Marine Laboratory, Plymouth) have 
shown, takes place progressively in the autumn. But 
the supply of nitrogen is soon replenished by the decay of 
organic material, especially following the fall in plankton 
60°F 
50°F 
40°F 
30°F 
20°F 
10°F 
Jan. Fes. Mar. Aprit May June Jury Auc. Sept. Oct. Nov. 
Fic. 1. Mean Monthly Temperatures of Sea and Air for 1903-1927. 
content in the autumn, and also bythe upwelling of supplies 
from deeper water. The scarcity of available food 
supply, therefore, may intensify the unfavourable physical 
conditions of the autumn and prove the last straw to the 
resistance of thalli already impoverished by other causes, 
though it is unlikely that this factor has a prolonged 
| | 
