40 



PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



Bokorny a has cultivated algre {Spirogyra, Zygnema, and Mesocarpus) 

 in culture solutions, in one of which there was no lime, in another no 

 magnesia, and in a third neither lime nor magnesia. These culture solu- 

 tions were kept in aluminum vessels to avoid any trace of substances 

 derived from glass. In the complete solution a normal formation in 

 every respect was noticed. In the solution in which lime was absent 

 the first phenomenon to occur was a decrease of the chloroplast, the 

 chlorophyll band of Spirogyra diminishing not only in breadth and 

 thickness, but also in length, and the original spiral finally becoming 

 a straight line parallel to the longer axis. Some starch, however, was 

 still produced, which proves that it is not the lack of organic matter 

 and of potash which here brings on this shrinkage, and that the 

 result can be attributed only to the absence of lime. In the solutions 

 in which magnesia and lime magnesia alone were absent the volume of 

 the nucleus decreased considerably, as well as that of the chlorophyll 

 bodies. The writer has repeatedly observed that Spirogyra majvscula 

 collected from swamps containing only traces of lime had very slender 

 chlorophyll bands and scarcely any starch, but that they contained 

 much stored-up albumin. When placed in culture solutions containing 

 a moderate amount of lime salts the bands soon became broader. 



Rudolph Weber 6 instituted a series of experiments with cultures of 

 peas under glass of different colors, and compared these plants with 

 plants grown in very faint light and with normal control plants. The 

 plants were grown in purified quartz sand and watered with culture 

 solutions in equal quantities. The culture was terminated after forty- 

 four days, because the plants under violet and green glass began at 

 that time to show signs of approaching death. The analyses of the 

 ash gave some interesting results, especially as regards the lime con- 

 tent, and are as follows: 



Comparative amounts <</' magnesia, lime and potash per thousand parts of dry matter <>f 

 ■norma! ami etiolated plants ami plants grown undt r different colored glass. 



Condition of plant. 



Norma] 



Etiolated 



Under green glass . . 

 Under violet glass. . 



Under red glass 



Under blue glass ... 

 Under yellow glass. 



Magnesia. 



Per <-i nl. 



10.2 



6.7 



S.3 

 8.5 

 9.5 

 8.8 

 9, 5 



Lime. 



Per c< nl. 

 32. 1 

 12.4 

 IS. 2 

 20. 2 

 24.3 

 30.2 

 30.3 



Potassa. 



Per ci nt. 

 4,s. 5- 



44. n 



5(1. 5 



45. (i 

 56 5 

 Gl.l 



53. 2 



a But. Centralbl., 1895, No. 14. The complete solution contained- 



Per cent. 



Potassium nitrate 0. 04 



Potassium sulphate 03 



IVTonopotassium phosphate 03 



( alciuni nitrate 03 



Magnesium sulphate 03 



&Land\v. Vers. Stat, 1875, Vol. XVIII, p. 19. 



