TRANSACTIONS OF SECTION K. 833 



before discharging it into the sea itself, the ammonia or nitrate will be absorbed, and 

 that the mixture of effluent and sea-water will then no longer provide nourishment 

 for the viva in the sea itself, and that consequently the sea- weed will be so much 

 reduced in quantity in the district as to cease to give rise to a nuisance. 



The stimulating effects of the ammonia or eflluent were evident from the rapid 

 evolution of oxygen from the surface of the sea-weed, which always occurred about 

 fifteen minutes after the addition of the polluting substance, and forms a pretty 

 experiment. 



In two cases the dissolved gases were extracted from the sea-water in which 

 the ulva was immersed (by boiling out with dilute sulphuric acid in vacuo) imme- 

 diately after adding the polluting material, and again some hours later, and 

 analyses made. The following results were obtained : — 



Ex^ieriment ok {BcujU'jhf). 



Immediately after adding 



Ammonium Chloride 

 (0'180 part per 100,000) Four Hours Later, 



(c.c. per Litre at N.T.P.) 



T = 1-1-4 T = 1.5-9 



CO 21-69 15-90 



O'... 11-41 14-84 



N-,... 9-79 9-88 



Loss of CO; - 5-79 c.c. Gain of 0, = 3-43 c.c. 



(About 2 c.c. of evolved oxygen gas were also collected.) 



Experiment 8b {Darkness). 



Immediately after adding 



Effluent Four Hours Later. 



(20 per cent.) 



Tzzl4-6 T = 14-8 



CO 63-59 . 66-44 



0„... 6-31 3-85 



n;... 11-90 11-74 



Gain of CO, = 2-85 c.c. Los3 of 0„ = 2-46 c.c. 



In oA the ulva had been in contact with the sea-water for a considerable time, 

 whereas in 8e fresh sea-water was used. 



The above analyses are interesting in several ways. First, in Experiment 5a, 

 the amount of oxygen found is greatly in excess of the value given by Dittmar 

 in the ' Challenger ' Reports for the volume of oxygen which one litre of sea- 

 water can take up when saturated with constantly renewed air at the existing 

 temperature, Dittmar's figure for 15° C. being 5-83 c.c. The action of the ^llva 

 is therefore, in a sense, to supersaturate the sea-water with oxygen under the 

 existing conditions. 



Secondly, the amount of carbonic anhydride found (in the same experiment) is 

 much less than that present in normal sea-water, Dittmar's average for the total 

 volume in sea-water being about 48 c.c. per litre, of which in all probability some 

 40 c.c. are in the form of soluble bicarbonate of calcium or magnesium. It is 

 evident therefore that the ulva gains its carbon from the carbonic anhydride of 

 these salts. 



Thirdly, the results of the experiment in darkness demonstrate in an interest- 

 ing manner the true respiration of the ulva, carbonic anhydride being evolved in 

 practically the same amount as the oxygen disappearing. 



6. Notes on Stellaria holostea and Allied Species. By John Paterson. 



Biology. — The shoots appear in early spring before the development of the 

 grasses. The leaves are arranged parallel to the stem axis in bud condition. They 

 open out and grasp the leaves of the grasses and other herbage as these develop, 



