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from the normal since it has assumed a lemon yellow color in the walls of 

 the bast layers and epidermal cells. The intensity of the discoloration is 

 connected with the quality of tannin. In observing differences in color one 

 must work (|uickly, since the coloring matter is soluble in water. 



All tliat has been said here of grain varieties may not be applied .without 

 limitation to other plants. As a general occurrence may be considered only 

 the fact that in all kinds of sudden death, the cell contents are abundantly 



Fisr. ]f)6. Beech Icavos 

 (Aflor V. Schii'iflor and Rou.ss.) 



retained, while they are for the most ])art used up in rcs])irati()n when the 

 leaf has lived out its life naturally. 



In order to emphasize the habitual differences in the manner of attack 

 of the vapors of sulfurous and hydrochloric acids we will give here illustra- 

 tions of injured leaves co])ied from the repeatedly cited works of v. Schroder 

 and Reuss. 



In Fig. 163 we see a leaf of a red beech taken from the vicinity of a 

 silver smelter, which had been injured by SD.. Fig. 164 shows a birch leaf 



