( 696 ) 
and cells containing many, few or no chromatophores. While I 
could determine the growth of such cells by measurement and could 
deduce from the size of the starch foci whether the starch content 
had increased or decreased, I was unable to obtain for one and the 
same cell an idea of the tannin content during the various periods 
of its existence. The usual reagents only permit of a single examina¬ 
tion being made, because during it the cells are killed. I had 
therefore to look for another method. 
I wondered whether methylene blue might perhaps satisfy the 
above requirements. According to Pfeffer 1 ) this substance forms a 
compound with tannin in the living cell, and this compound separates 
as a tine blue precipitate. For various physiological investigations 
Pfeffer strongly recommends aniline dyes particularly methylene 
blue. Of this he says i.a. the following*): “In alien Fallen werden 
also Methylenblau und andere Farbstoffe wertvolle Reagentien sein, 
mit deren Hulfe, ohne Schadigung Aufschliisse fiber Vorkommen und 
Verteilung gewisser Korper in der Zelle zu erhalten sind. Mit solcher 
vielseitig ausnutzbaren Methode lasst sich unter richtiger Erwagung 
naeh vielen Richtungen hin eine Kontrole des jeweiligen Zustandes 
des Zellsaftes und der Veranderungen dieses im Laufe der Ent- 
wicklung erreiehen.” When dilute solutions are used, the penetration 
of methylene blue into the body of the plant and its accumulation 
in the cellsap continue, according to Pfeffer*), without any harm 
to life and even when complete saturation has taken place, it is 
still innocuous. Spirogyra was one of the objects with which Pfeffer 
experimented. 
Pfeffer s experiments were repeated by me a few times with 
Spirogyra maxima , but with very unsatisfactory results. Even after 
several days only a slight granular precipitate was obtained in the 
cells, and at least the greater part of the tannin remained in solution; 
moreover, even very dilute solutions were found to be harmful. 
I cannot therefore agree with Pfeffer in praising his method of 
investigation, and after this disappointment a better method was 
sought. 
Preliminary experiments were earned out on Spirogyra maxima 
wdh various tannin precipitant, such ^ alkaloids, antipyrine, am¬ 
monium vanadate and many others. Of all the substances examined, 
catfeme and antipyrine were found to be the least harmful, and 
ere ore e action of these two substances was investigated more 
9 i. c. P . ioo. 
2 ) L c. p. 191. 
1. c. p. 195, 196 aiu* 19?, 
