336 



slowly succeeding death, an alkaline reaction, by which the indoxyl soon oxidises lo 

 indigo-blue, which therefore precipitates in these cells alone, and not in the quickly 

 killed nor in the living cells. Put into ammoniac-vapour the living, as well as the 

 dead part oft the Polygonum-leai remain uncoloured, in opposition to the woad-leaf, 

 this, after the preceding, requires no further elucidation. 



Of course, these phenomena would find a somewhat simpler explanation if they 

 could be brought back to the action of an oxidase, present from the beginning. But 

 an oxidase, producing indigo from indoxyl is, as said, not to be found. 



To conclude I wish to observe, that some ether phenomena, which are attributed 

 to the effect of a »wound-irritation«, for instance, the formation of starch and of red 

 pigfment, as also the development of warmth in hurt parts of plants, possibly repose 

 also on alkali-formation in or near the damaged cells. 



