256 Pennington — A Chemico-PJiysiological 



is interesting to note in connection with the statements 

 made by these observers that, in the experiments made on 

 Spirogyra, it was the yellow only which caused a marked 

 lengthening when the red, orange and yellow rays were 

 separated, though under the orange-yellow glass the action 

 of the yellow rays was not sufficiently retarded by the 

 presence of the others to prevent the cells elongating. 



Rauwenhoff * states that less tannin is found in etiolated 

 leaves and plants than in green ones. Here, too, the 

 behavior of the yellow culture accords ; tannin is entirely 

 absent. 



Looking at the question of the action of light on plant 

 growth, from the chemical changes noticed in Spirogyra, 

 we see that assimilation, though in a more or less modified 

 form, can occur when none of the light rays are absorbed 

 by the green coloring matter. Also, that such absorption 

 may or may not be accompanied by assimilation. 



The blue and violet rays seem to act as checks to the 

 great activity of the yellow, and perhaps to the orange, 

 preventing the too rapid transformation of starch into sugar, 

 upon which the rapid growth in length apparently depends. 



The Action of Palladious Chloride on the 



Living Cell. 



While studying Spirogyra micro-chemically palladious 

 chloride was used as a reagent. The action of this sub- 

 stance upon the living cell demonstrated so clearly certain 

 morphological features, that a more careful examination 

 of its behavior was made. It was found that a solution 

 containing 0.1478 grams palladious chloride in 100 cc. dis- 

 tilled water fixed the cell instantly, and with the minimum 

 amount of distortion. The protoplasm was slightly browned, 

 making the nucleus and its threads the more easily seen. 

 If the solution be diluted until it contains only 0.001478 

 grams palladious chloride in 100 cc.,the morphological 



* Ann. d. Sci. Nat, Ser. 6, t. v., (1877). 



