736 



anKjiig the healthy ones. The red hrowii. which in the bei^inning was very 

 bright, soon turned into a gray l)r()wn. The needles kept this cohjr until 

 they fell, about two weeks later, but this took place only on greatly injured 

 branches. It was found in the discolored places of the slightly injured 

 needles, remaining on the branches, that the walls of some groups of meso- 

 phyll cells near the epidermis had turned a faded \o reddish yellow, while 

 the contents had lost their color and finally with a complete disorganization 

 of the walls had dried up. In this they not infrequently passed through a 

 stage of foamy consistency. For some time after the action of the gas the 

 guard cells of the stomata seemed to have become discolored up to the 

 healthy tissues only in the zones of transition whereby their walls had turned 

 a brownish yellow. The epidemiis was slightly browned ; the sub-epidermal 

 prosenchymatous fibres were found to be colorless. The mesophyll near 

 the brown places remained green and had either a tlocculent green content 

 or the chloroplasts were united into lumi)s. Healthy tissue adjoined this 

 immediately. 



At places more strongly injured the vascular bundles were also affected 

 and discolored just as from sulfurous acid, but the color tone of the injured 

 needles was only rarely a reddish brown. They were generally a yellowish 

 brown and less hard, a fact distinguishing them from needles affected by 

 SO^. The slight amount of difference is of less moment here because, as 

 said above, in general injuries from bromine occur as a rule in connection 

 with those caused by sulfurous acid. 



