238 W. C. ALLEE. 



The pH averages the same in the wharf pilings and open water 

 associations. The rockweed association comes next with the 

 association of exposed rocks very near it. The pH values from 

 the exposed rock association is higher than would be expected for 

 the entire coast because only one of the three places in which it 

 was studied was free from the influence of nearby submerged 

 vegetation. Under entirely typical conditions the average pH 

 in this series should likewise arrange the series in the same order 

 as the other factors measured. 



The rankings given in the table are based upon the extent of 

 variation from conditions known to be characteristic of open 

 water. The sum of the ordinal ranks, a poor enough method of 

 averaging, shows a gradual increase corresponding to the ecolog- 

 ical age of the associations. 



The range of these four factors (Table XV.) tends to increase 

 with the age of the association. This is not true of each factor 

 taken separately, nor is the increase in total amounts in regular 

 order, in that the rockweed association on this basis precedes 

 the exposed rock association, when it would be expected to 

 follow it. 



In addition to the absolute range the data from these extremes 

 show another set of relations not given in averages, that is the 

 relative position of the extremes. In salinity of the open water 

 the lowest record is fairly high and, while the upper extreme of 

 salinity remains approximately constant, there is a general fall 

 in the lower limit as one passes from open water to the older 

 associations. 



In the temperature series the characteristic change is in the 

 matter of the greater maximum in the older associations. With 

 pH, the young associations have practically no change, the older 

 ones have an increased upper limit due to the action of plants, 

 while the oldest ones show a decided decrease in the minimum on 

 account of the acid -giving muck which is deposited in them. 



A combination of the rankings based on the departure of 

 average low tide conditions from those known to occur in open 

 water and on amount of variation between observed extremes, 

 places the associations in order of their ecological age, with the 

 exception of the rocks and rockweed associations which are 

 placed together. If in place of an index figure based on amount 



