632 BOWMAN— ECOLOGY AND 



In 1915 a series of cultures was made on hyperconcentrated sea 

 water of 140 per cent, concentration. The transpiration rate records 

 for the culture showed a very slow rate of transpiration and in fact 

 the whole metabolism of the plants was so retarded that the plants 

 slowly yellowed, dropped the leaves and died after a few weeks. 

 The rate on the basis of Stahl's method was 5.66, i. e., approxi- 

 mately there was required 5.66 minutes to change the indicator of 

 the transpirometer. 



In addition to the cultures in water, there was a series planted in 

 shell sand and merely kept moist with salt water, but also kept in the 

 laboratory sheltered from the direct rays of the sun, wind and rain. 

 Another series, however, was placed in boxes of sand, merely kept 

 moist but placed on the landing dock of the laboratory in full glare 

 of sun, etc. This situation most nearly approached the living condi- 

 tions of Rliiaophora seedlings drifted up on the beaches of the Tor- 

 tugas Islands. As there are no mangroves in these islands except 

 two young trees in a very sheltered position on Garden Key, an 

 inquiry into the physiological behavior of these drifted plants was 

 attempted to learn why the mangrove does not survive in this group. 

 This subject will be discussed in the light of the above experiments 

 in the chapter on ecology. However, it suffices to say here that the 

 hard conditions of these cultures proved too much for the seedlings 

 and one pair of tiny lea.ves would unfold after another with very 

 short internodes and each pair would successively be burned up by 

 the intensely hot sun and the glare of the reflection of the white 

 sand in which they were planted together with the greatly reduced 

 absorption from the merely moist, coarse, porous substratum. After 

 a month of this heroic attempt at growth, the seedlings succumbed 

 when the reserve food in the hypocotyl was exhausted, no foliage 

 being put forth during their brief existence that attained sufficient 

 size on which to take transpiration rate records. 



In a previous season at Tortugas a number of cultures was 

 made of seedlings planted in jars of the Fort Jefiferson moat mud, 

 but the water was not siphoned from these cultures daily and a 

 fresh supply put on, so that in a short while the water became so 

 charged with HoS gas that it produced a toxic efifect on the plants, 

 from which they soon died. This toxic effect of the hydrogen 



