1913.] PUBLIC DOCUMENT — No. 31. 51 



Hartig ^ mentions that Camellias, azaleas and ivy arc very 

 sensitive to escaping gas, the least sensitive being palms and 

 Dracirnas. It would appear that the higher plants are more 

 susceptible to gas than the lower ones. This might be explained 

 on the assumption that the lower plants, being descendants of 

 very old types which in past ages may have been adapted to 

 different atmospheric conditions, possibly inherit a wider range 

 of adaptability, with consequently less liability to injury. 



Effects of Illuminating Gas on Caeolina Poplars. 



Our attention has been called at different times by Mr. James 

 Walker, of the jSTewark Shade Tree Commission, Newark, 

 N. J., to a peculiar effect which poisoning from illuminating 

 gas has on Carolina poplars (Fopulus deltoides Marsh).- This 

 tree is used extensively for shade in New Jersey, but has re- 

 cently come into disrepute owing to the havoc which its vigorous 

 root system raises with sewers. Some of these characteristic 

 toxic effects consist in a splitting of the bark and swelling and 

 bulging of the tissue near the lesions, and later a slimy, muci- 

 laginous mass exudes from the cracks. 



This last season we examined a Carolina poplar which dis- 

 played, in addition to the usual symptoms of gas poisoning, 

 this peculiar swelling and cracking of the bark, and some of 

 the tissue was gathered for histological examination. The tree 

 in question was 7 or 8 inches in diameter near the base, and at 

 the time of observation, in common with most trees affected 

 by gas poisoning, had no leaves. The bark, cortex, etc., on the 

 trunk towards the source of absorption showed three or four 

 vertical cracks or lesions l/o to 21/^ feet long. The bark on the 

 sides of these cracks was bulged out considerably, and examina- 

 tion showed a thick layer of soft, parenchymous tissue extend- 

 ing to the wood and a]iparently derived from the cambium 

 zone. This tissue at the time of observation was ])erfectly 

 white and fresh in appearance, was easily broken and appar- 

 ently as delicate as the tissue of an apple. Later the tissue 

 turned brown and disintegrated and became slimy in appear- 



' R. Hartig, "The Diseases of Treos." 



2 We have heard the opinion expresspri at different times tliat Carolina poplars are immune 

 to gas poisoning, but there is no foundation for tiiis statement. 



