1 j6 Schunck and Brehner . — On the A ction of A niline 
tillates obtained from the watery extracts of ash and mint 
leaves showed no trace of crystals on the addition of aniline 
and standing, even after the lapse of a week,, so that it appears 
that the active agent contained in the extract, whatever it be, 
does not pass over with the vapour of water. 
It remains for us to say a few words as regards the bearing 
of our experiments on the vexed question of the presence of 
active oxygen, in some form or other, in the cells of plants. 
This question has been much debated, some observers main- 
taining that the presence of active oxygen may be easily 
demonstrated, while others assert that it is entirely absent. 
We are inclined to think that this want of accord is due to 
the fact that active oxygen is sometimes present, sometimes 
absent, owing to some cause or causes which are unknown, 
and are not even hinted at by those who have treated the 
subject. In one of his numerous memoirs on active oxygen 
Schoenbein states 1 that the expressed juices of many plants, 
especially of dandelion and lettuce, give a reaction similar to 
that of hydrogen peroxide with tincture of guiacum and with 
acidulated starch iodide solution. According to Pfefifer this 
reaction would not indicate the presence of hydrogen peroxide 
within the living cell, since expressed juices may have, and 
have indeed been found to have the property of activating 
passive oxygen. In his interesting research entitled ‘ Beitrage 
zur Kenntniss der Oxydationsvorgange in lebenden Zellen 2 ,’ 
Pfefifer proves conclusively that the cells of the plants he ex- 
amined do not contain active oxygen in the form of hydrogen 
peroxide. We repeated two of Pfefifer’s experiments and were 
able to confirm the results arrived at by him. In the case of 
the staminal hairs of Tradescantia , using a solution containing 
o '25 per cent, of hydrogen peroxide, we observed the complete 
precipitation of the colouring-matter with mere retardation of 
the protoplasmic streaming ; the latter returning in full vigour 
after the surplus hydrogen peroxide had been washed out. In 
the case of only one cell did we see any change in the colour 
1 Journ. f. prakt. Chemie, 102, 155. 
2 Abh. d. math.-phys. Cl. d. k. Sachs. Ges. d. Wiss. xv. 1889. 
