46 BOTANICAL MICROTECHNIQUE. 



within the living cell. He showed first that the peroxide 

 may be taken up by living cells without harm and that it 

 often produces in them, even when in very small quantity, 

 plainly visible reactions, which do not otherwise occur in 

 living cells. 



Pfeffer used first for these researches plants whose color- 

 less cell-sap is colored by the oxidizing effect of the peroxide,. 

 as, e.g., the epidermal cells of the stem and root of seedlings 

 of Vicia Faba or the root-hairs of Trianea bogotensis. In 

 these the peroxide produces a browning of the cell-sap which 

 is usually followed by the separation of red-brown or almost 

 black granular masses, as is shown in Fig. 17. 

 Here is figured a part of an epidermal cell from 

 the stem of Vicia Faba, which has lain five hours 

 in a solution of peroxide of hydrogen, prepared 

 by mixing ten parts of pure water with one part 

 of a commercial peroxide solution already six 

 months old. 



66. Pfeffer also worked with cells which have 

 naturally a colored cell-sap, like the stamen-hairs 

 of Tradescantia virginica. In this case the blue 

 FIG. 17 .-part of cell-sap is wholly bleached by the peroxide or 

 ceii C of "tThe takes a yellow-brown or vinous-yellow color. 

 " Bleaching by the peroxide taken up may also 

 be observed in cells whose protoplasm has been 



in peroxide of , r 



hydrogen so- previously colored blue by cyanm. 1 he root- 

 hairs of Trianea bogotensis are well adapted for 

 these experiments. In their protoplasm, when in a very 

 dilute solution of cyanin, prepared by warming that dye 

 with water, various blue differential stains were evident in 

 from three to fifteen minutes, and were destroyed by perox- 

 ide of hydrogen in less than a minute. 



67. It may be remarked that Pfeffer worked with solu- 

 tions of from .01$ to \% of the peroxide. Since the com- 

 mercial peroxide always contains some free hydrochloric 

 acid to increase its keeping quality, it must be neutralized 

 with sodium bicarbonate ; and Pfeffer adds this in slight 

 excess. 



