PHYSIOLOGY OF THE RED MANGROVE. 631 



sun and rain. However, during the long, still, calm days of June 

 and July there is very little atmospheric variation in the Tortugas 

 climate. The greater part of these two months is made up of clear, 

 sunny days with almost no wind. The average wind velocity for 

 the region, according to the U. S. Weather Bureau Records from 

 Key West, is 9.6 miles per hour for the year, but most of the gales 

 occur in the fall and winter months, September and October being 

 called the " hurricane months." 



The average temperature for the year is 76.8° F. with a maxi- 

 mum of 88° F. and a minimum of y']° F. during the months in 

 which these tests were made, while the average relative humidity 

 for the whole general region is about 'j}^ per cent. 



In both the soil and the water concentration series of experi- 

 ments it was found advisable to siphon off the water from each cul- 

 ture jar daily. In doing this, two objects were attained — a fresh 

 supply of water containing the various gases, etc., in solution was 

 furnished the roots of the plants, simulating the tidal action of the 

 sea in the natural beds in the mangrove swamps and also by this 

 means the mosquito larva were removed to a large extent, the cul- 

 tures of plants in fresh water and the higher dilutions of salt water 

 Ipeing an ideal place for the breeding of mosquitos if left undis- 

 turbed. 



In the water concentration series of cultures several hundred 

 seedlings were potted in the jars similar to the above described soil 

 experiment cultures. The soil used however to anchor the seed- 

 lings was uniform for all the series, that is, only the Tortugas shell 

 sand was used. 



The water concentrations emplo[)'ed for the series were as 

 follows : 



Series A — 100 per cent, fresh water. 



Series B — 75 per cent, fresh water. 



Series C — 50 per cent, fresh water. 



Series D — 20 per cent, fresh water. 



Series E — 10 per cent, fresh water. 



Series F — 5 per cent, fresh water. 



Series G — 100 per cent, salt water. 



