436 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 4 



ture, trunk temperature in a healthy tree 

 and pressures in a healthy tree and in a 

 wetwood-affected tree was studied from 

 October 5, 1943, to January 13, 1944. 

 Curves in fig. 30, which are typical, show 

 the readings for November 16. Air and 

 trunk temperature readings are given in 

 degrees Fahrenheit, pressure readings from 

 the healthy tree as millimeters of water, 

 and pressure readings from the wetwood- 

 affected tree as pounds per square inch. 



The air temperature curve shows a 

 gradual increase from 8:00 a.m. until 1 :00 

 P.M., when the temperature reached 77 

 degrees F. Opening the greenhouse ven- 

 tilator between 1 : 00 and 1 : 10 p.m. caused 

 the air temperature to drop from 77 to 70 

 degrees F. This drop was followed by an 

 increase to 71.5 degrees at 1:25; then 

 the air temperature declined to 57.5 

 degrees F. at 3:15 p.m., after which it in- 

 creased to 65 degrees at 3:45 p.m. The 

 pressure curve and the trunk temperature 

 curve for the healthy trees are similar to 

 the air temperature curve except that the 

 trunk temperature curve continues to de- 

 cline between 3:15 and 3:45 p.m. Rey- 

 nolds (1939) found temperatures in pop- 

 lar and Cottonwood to be influenced great- 

 ly by air temperatures. Pressure in the 

 wetwood-affected tree became apparent by 

 10:00 a.m. and increased until 1 : 15 P.M. 

 This pressure stood at a maximum of 5.2 

 pounds from 1:15 to 2:00 P.M., but de- 

 creased as the air temperature dropped be- 

 low 68.5 degrees F. 



The average of the maximum air tem- 

 perature readings taken in the greenhouse 

 was approximately 83 degrees F. in Oc- 

 tober, 73 degrees F. in November, 66 

 degrees F. in December and 71 degrees F. 

 in January, while the average of the maxi- 

 mum trunk temperature readings taken 

 was approximately 74 degrees F. in Oc- 

 tober, 70 degrees F. in November, 68 

 degrees F. in December and 71 degrees 

 F. in January. As no continuous recording 

 devices were used, the maximum tempera- 

 tures recorded in many cases may not have 

 been the actual maximum temperatures. 

 Air temperatures of 66 to 73 degrees F. 

 are not sufficiently below the optimum 

 temperature for the wetwood organism 

 (75.2 to 86.0 degrees F.) to stop fermen- 

 tation. Pressures that could be measured 

 with a gauge were present in the wetwood- 

 affected elm until the tree became dormant 



about December 1. The average daily 

 maximum pressure was 8 pounds in Octo- 

 ber and 4 pounds in November, but in De- 

 cember and January the pressure, if any 

 was present, was too low to register on 

 the gauge. 



The pressure in the healthy tree did not 

 decrease as did that in the wetwood-affect- 

 ed tree and was not noticeably affected by 

 dormancy. The healthy tree had an aver- 

 age daily maximum trunk pressure of 6.7 

 mm. in October, 7.9 mm. in November, 

 4.8 mm. in December and 6.7 mm. in 

 Januar>^ 



Gas Analysis 



Gas produced in wetwood-affected elms 

 was analyzed in the field for carbon dioxide 

 and in the laboratory for carbon dioxide, 

 oxygen, hydrogen, methane, carbon mon- 

 oxide, illuminants and nitrogen. The gas 

 samples analyzed were from trees ranging 

 from 5 to 12 inches d. b. h. Field analyses 

 for the per cent of carbon dioxide in the 

 gas were made by collecting approximate- 

 ly 24 ml. of the gas in Smith fermentation 

 tubes over water and by absorbing the 

 carbon dioxide with N/5 sodium hydrox- 

 ide. 



The gas samples analyzed in the field 

 were collected in August, October and 

 November, 1942, and in June, July and 

 August, 1943. The analyses tended to 

 show that in August the gas contained 

 more carbon dioxide than it did in pre- 

 ceding or succeeding months. The per cent 

 of carbon dioxide in different trees varied 

 considerably during any one day. There 

 was no correlation between the diameter 

 of the trunk and the per cent of carbon 

 dioxide in the gas. For instance, each of 

 two gas samples collected on August 19, 

 1943, one from a tree 12 inches d. b. h. and 

 one from a tree 5 inches d. b. h., contained 

 19 per cent carbon dioxide. Gas was not 

 present in sufficient quantities to be collect- 

 ed for analyzing from December, 1942, 

 to May, 1943. 



Samples of gas were analyzed in an 

 Orsat apparatus, July 2, 1943, and found 

 to consist of approximately 46.4 per cent 

 methane, 33.8 per cent nitrogen, 14.3 per 

 cent carbon dioxide, 4.5 per cent oxygen 

 and 1.0 per cent hydrogen. Carbon mon- 

 oxide and illuminants were not present. 

 The amount of hydrogen recorded (1.0 



