260 



BOTANICAL GAZETTE 



[OCTOBER 



O O 



attached to each slide at the water level. As many as fifty to a 



hundred zoospores were commonly 

 . found arranged in a row across the 

 " slide, so that subsequent observa- 



tion was an easy matter. The slides 

 were thoroughly rinsed in distilled water and 

 transferred to the solutions. The solutions 

 were contained in glass tumblers, in which 

 the slides were placed in an upright position, 

 care being taken to have the zoospores always 

 at the same depth below the surface. The 

 volume of the solution, ioo cc , was very large 

 compared with that of the zoospores. The 

 tumblers were covered with glass plates to 

 exclude dust and hinder evaporation. Under 

 these circumstances the plants thrive excellently 

 and in favorable solutions produce normal 

 mature fruit. 2 



The average results of six series of experi- 

 ments are given in Table III and illustrated in 

 fig. i. The figure shows clearly how a mixture 

 of two poisonous substances may produce a 

 solution as harmless as distilled water. 



The species of Spirogyra employed is a large 

 one of the majuscula type. The material was 

 transferred from the pond directly to distilled 

 water; after being rinsed in this it was placed 

 in covered glass dishes containing each 200 cc of 

 solution. 



It will be seen that these results agree in 

 the most striking way with those already 

 described for marine plants. 



Further experiments were made with a 

 variety of other algae, including a species of 

 blue-green alga (Oscillatoria), Chlamydomonas, 

 Closterium and two other species of desmids, 



2 Cf. OSTERHOUT, Extreme toxicity of sodium chloride and its prevention by 

 other salts. Jour. Biol. Chemistry 1:363. 1906. 



FIG. i. Growth of 

 zoospores of Vaucheria 

 during 25 days in various 

 w/ioo solutions. The 

 quantities are stated in 

 cubic centimeters, the 

 length in millimeters, 

 and the gain in length 

 in per cent, i, distilled 

 water, length 9.4, gain 

 5000. 2, NaCl 1000 

 + CaCl 2 10, length 9.4, 

 gain 5000. 3, NaCl, 

 length 0.18, gain o. 4, 

 CaCl 2 , length 0.18, 

 gain o. 



