LETHAL GASES 195 



appreciable effect on roots. Concentrations of 500 and 1000 ppm retarded 

 the emergence of seedlings, burned and usually killed the tops and roots of 

 plants eventually. A combination of watering and syringing generally pro- 

 duced greater and more rapid injury than watering the soil alone. Syringing 

 the tops usually was somewhat less injurious than watering the soil with 

 the same solutions. Injury from all treatments was m most cases more 

 serious and more rapid in the greenhouse than m open cold frames, and 

 worse under bell jars m the greenhouse than on the open greenhouse bench. 



"Tops of plants grown in a mixture of equal parts of loam and sand were 

 retarded in top growth by solutions of 50 ppm and 100 ppm but not by 

 5 ppm. Roots were never injured in this soil. Plants grown in sand were 

 retarded in root and top development by solutions of 5, 50, and 100 ppm 

 chlorine, the degree being somewhat in relation to the concentration of 

 chlorine in the solution. Chlorinated water applied to sand and to loam 

 soil for three weeks had no significant effect on acidity of the media. 



''Roots from tomato cuttings in chlorinated water were retarded in size 

 directly as the chlorine concentration mcreased from 10 ppm, but they were 

 not affected by 5 ppm. Cut flowers were not affected by free chlorine ui 

 water up to 10 ppm. Fifty parts per million mjured gerbera and snap- 

 dragons but not gladiolus or roses. Cahomba and Elodea were discolored 

 by chlorinated water containing 3 ppm in one week when the water was 

 refreshed daily. A concentration of 5 ppm produced injury m two days 

 and death in four days." 



From what has been said above, it is evident that CI2 in the air is much 

 more toxic to land plants than when in water solution; it takes less than 

 1 ppm by volume of CI2 in the rare medium, air, to spot more sensitive 

 plants, whereas it requires several ppm by weight in the dense medium, 

 water, to injure these plants. The CI2 enters the tissue of land plants 

 through the stomates much more readily as a gas than it does through the 

 general cuticular structure in solution. The greater injury from keeping 

 plants sprayed with chlorinated water under bell jars or in greenhouses as 

 compared with open air was due to gas escaping from solution and being 

 held about the plants by the enclosures so it could enter through the 

 stomates. Since water plants, such as Cahomba and Elodea, are poorly 

 cutinized, CI2 in solution enters the plant readily. 



Concerning the effect of chlorinated water on goldfish the authors 

 say: ^^^ p"^ "Under the conditions stated in the text goldfish were killed by 

 chlorine solutions of 1.5, 2.0, and 3.0 ppm where the water was changed 

 daily. Where water was constantly renewed, concentrations of 1.0 and 

 1.5 ppm were toxic. Fantail variety appeared to be less resistant than the 

 Common variety of goldfish, while the Common variety was less resistant 

 than the Shubunkin variety. Aquatic plants appeared to counteract ui 

 some degree the toxic effects of chlorinated water on fish." 



The authors point out that Yonkers city water at the tap frequently 

 contains 0.5 ppm of residual CI2, occasionally 1.0 ppm, and rarely 1.5 ppm. 



