Study of Spirogyra nitida. 



Not only do we find the fundamental constituents of the 

 cell undergoing modifications, but other products, such as 

 the cell crystals, are much altered by different light rays. 

 While there is, iu all probability, a direct connection be- 

 tween the formation or disappearance of these bodies and 

 the General activity of the cell, I have not been able to for- 

 mulate it from the above experiments. 



In yellow light the obliteration of the crystals is almost 

 complete, while it is less marked in orange and red. When 

 the plant is kept in darkness without a sufficient oxygen 

 supplv the same breaking down occurs. As etiolation 

 implies also starvation, it might be supposed that the solu- 

 tion of the crystals provided nutritive material. Yet in 

 orange and red light there is a diminution in the number 

 of crystals, though the cells are well nourished. 



Green light tends to promote the production of tartrate 

 crystals, increasing them both in number and size, though 

 here also oxalate crystals were used up. Weber* finds the 

 greatest absorption of ash constituents to take place when 

 the plant is in white light ; it is somewhat less in yellow, 

 then follow red, blue and violet, decreasing in activity 

 as the refrangibility of the rays, but green gives the 

 lowest ash content. These results were based upon the 

 action of the light which passed through colored glasses, 

 none of which were monochromatic. One would infer 

 from the large crystals of the green culture that an exten- 

 sive absorption of inorganic constituents was here taking 

 place, while results from the yellow, showed either very 

 few or no crystals whatever, leading to the opposite view. 



A number of observations have been made which show a 

 similarity between yellow light and darkness. Sachs and 

 Kraus have found that etiolation tends to produce long in- 

 ternodes ; and rays of low refrangibility do the same. Cor- 

 responding to the internodes we have the individual cells 

 of the Spirogyra thread, and, as we have seen, these under 

 yellow light attain to three times their normal length. It 

 *Landw. Vcrsuchstat., Vol. 18 (1875). 



