1913.] PUBLIC DOCIBIENT — No. 31. 53 



and other trees to trap insects, injury often results to the tissue, 

 with swellings and distortion where the substances come in 

 contact with the bark. We have seen many trees affected in this 

 way in the eastern part of the State, where much use has been 

 made of banding substances for the extermination of the gypsy 

 moth. Their effect is more pronounced on Carolina poplars 

 than on other trees, and it is not improbable that this cracking 

 and abnormal formation under the bark results from decreased 

 turgescence of the cell and destruction of the outer tissue, thus 

 relieving the tension on the inner tissue and causing the cam- 

 bium to divide. With the release of the pressure outwards, it is 

 natural fcr this tissue to extend in this direction, thus ruptur- 

 ing the outer bark. The absorption of the gas may have killed 

 the tissue exterior to the cambium layer before the cambium 

 was affected. In this way, the tension of the outer tissue being 

 diminished, a stimulation of the cambium cells results. 



The poisonous constituents of gas have a direct stimulating 

 effect on the cells during the incipient stage of poisoning, as 

 observed in the case of willow cuttings, etc. ; but in this instance 

 it would appear that the excessive development of the cambium 

 was caused by the diminished tension of tlie cortical tissue. 



Stimulating Effects of Illuminating Gas on Willow 



Cuttings. 



For many years we have been studying the effects of differ- 

 ent gases on the functions of plants, and during this time we 

 have made many experiments relative to the effects of water 

 charged with illuminating gas on the development of willow 

 cuttings. It is well known that there are many chemical sub- 

 stances which stimulate plants. Even the most violent poisons, 

 if administered in certain dosages, will greatly increase plant 

 activities ; for instance, ether is well known to cause latent buds 

 to blossom, and some use is made of it by commercial florists. 



Illuminating gas is a deadly poison both to the foliage and 

 root systems of plants; but when administered under certain 

 conditions is a great stimulant. Latent willow cuttings grown 

 in water charged with illuminating gas for a few moments 

 every day or two showed a greatly increased development, pro- 



