438 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 4 



sugars in the leaches produced by auto- 

 claving healthy sapwood and healthy 

 heartwood. Ogilvie (1924) found no 

 sugar, or only traces of it, in the clear 

 fluid from "water-soaked wood" of elm. 



The pH of Sap 



To' compare the pH of sap from wet- 

 wood-affected elms with the pH of water- 

 soluble materials in the wood and bark of 

 healthy trees and in the wood of trees 

 affected with wetwood, each of the tissues 

 named was soaked in distilled water and 

 the resulting leach, containing water- 

 soluble materials, was tested for its pH. 

 Ten samples of sap and 10 samples of 

 wetwood leach were alkaline, pH 7.9, 

 when tested with indicators in the field. 

 Five samples of leach from healthy wood 

 and five samples of leach from healthy 

 bark were acid, pH 6.3. The distilled 

 water used in these tests was neutral to 

 slightly acid. 



The pH values of wetwood sap and of 

 wetwood leaches, and of healthy wood and 

 healthy bark leaches, were determined 

 with the Youden apparatus in the labora- 

 tory on several occasions and are given in 

 table 4. Both sap and leach from wetwood- 

 affected elms were alkaline, averaging pH 

 7.67 and 7.39, respectively. The leaches 

 from healthy wood and bark were acid, 

 averaging pH 6.35 and 5.89, respectively. 

 These data indicate that sap in healthy elm 

 wood and bark is acid, while sap in wood 

 affected with wetwood and also the water- 

 soluble materials from wood affected with 

 wetwood are alkaline. This is in general 

 agreement with the findings of Ogilvie 

 (1924), who reported the brown and red 

 flux from elm to have a pH of 9 or above, 

 and of Crandell, Hartley & Davidson 

 (1937), who found wetwood-affected 

 tissues of elm and other trees to have a 

 higher pH value than either live sapwood 

 or true heartwood. 



Additional pH tests were made on fil- 



Table 4. — The pH of wetwood sap and of leaches of wetwood, healthy wood and healthy 

 bark of elms. The readings were obtained with the Youden apparatus, with platinum electrodes. 



Date Collected 



July 23, 1941. 



August 15, 1941. 



November 12, 1941*. 



August 11, 1942. 



Average pH. 



Tree No. 



1 



2 

 3 

 4 



5 

 6 



7 



10 



11 

 12 

 13 

 14 

 15 



16 

 17 

 18 



Wetwood 

 Sap 



7.43 

 7.36 

 7.80 

 8.34 



7.56 



7.11 



7.87 

 7.31 



7.62 

 7.36 

 7.70 



8.55 

 8.00 

 7.40 



7.67 



pH Value 



Wetwood 

 Leach 



7.39 



Healthv 

 Wood Leach 



Healthy 

 Bark. Leach 



6.35 



5.91 

 5.94 

 5.75 

 5.86 

 6.01 



5.89 



*The materials collected on November 12, 1941, were tested with indicators as well as with the Youden apparatus. 

 All wetwood sap and wetwood samples tested approximately pH 7.9, while healthy wood and bark samples tested 

 approximately pH 6.3. 



