735 



Young branches become corky on the side affected and show fine cracks. 

 Any existhig air roots dry up. 



When the action of the asphalt fumes ceases, the leaf's attempt to heal 

 itself at once become apparent. In case the palisade parenchyma has been 

 only a little, if any, affected, it may elongate somewhat and slightly push out 

 the epidermis, which has collapsed to a state of irrecognisability. If, how- 

 ever, the palisade layer has also died the healthy underlying mesophyll 

 develops a perfectly regular layer of flat cork cells. The same process may 

 be noticed on the leaf stems : the brown, dead, ruptured, outer cork and 

 parenchyma layers, together with the hard bast bundles which at times have 

 also succumbed to the necrosis, are separated from the healthy tissue by a 

 broad cork band which in extreme cases extends as far as the cambium. 



Vitis vinifera suffers sooner and more than does Ampelopsis, so that its 

 leaves, at times, are curled entirely out of shape and perforated. In this it 

 was observed that in places lightly affected the guard cells of the stomata 

 had suffered first. Other plants behaved differently ; in regard to these, 

 reference must be made to my original work on the subject. The corrosion 

 of the epidermal cells, however, may be cited as the universal characteristic. 



As in all injuries due to gaseous bodies, the fact that the injury is 

 chronic, or acute, determines the results ; in the former case, with slower 

 action, the organ affected can remain alive for some time by its counter 

 action and may slowly live out its life. In this the characteristics differ 

 frOm those found when the action is that of more highly concentrated gas 

 waves, which result in a rapid death. Thus, for example, in the slow death 

 of spruce needles, a strong, red discoloration of the cytoplasm of the guard 

 cells and later, in fact, of their walls was perceived in the still green parts, 

 but not if the injury was acute. The walls of the vascular bundles element 

 also discolored ; as always happens from asphalt fumes, the cell walls suffer 

 especially quickly. This is seen very well in the older fir needles which 

 acquire a metallic lustre. 



Bromine. 



In the ordinary industries in which bromine is produced injuries due 

 to bromine alone may scarcely be spoken of because, as a rule, sulfurous 

 acid works with it. At considerable distances from the factories the 

 bromine may still be perceived by its odor, but no decided injuries from 

 the acid. Therefore, any description of natural occurrences in the neigh- 

 borhood of bromine factories may be omitted here and only the behavior of 

 plants under the artificial action of intense bromine fumes be described. 

 I carried out experiments as follows for 4 days : — 



Small, well-rooted spruce saplings in pots were exposed several hours 

 each day to gaseous bromine, being left out of doors between times. The 

 branches nearest the bromine sources naturally suffered most and all their 

 needles turned brown. On the less injured branches many needles were 

 found to be partially brown from the tip back, while on the branches furthest 

 away from the course of the bromine only a few brown needles were found 



