August, 1945 



Carter: Wetwood of Elms 



427 



One of them, however, showed some 

 browning of the interveinal tissues of the 

 leaves on the side of the tree directly 

 above the incision. In all of them, grayish 

 brown streaks typical of wetwood devel- 

 oped in the last-formed spring and early 

 summer wood, extending 4 to 9 inches up 

 the stems and 3 to 6 inches down the 

 stems from the incisions. 



The three seedlings which had incisions 

 made in their stems under sap developed 

 wilt. A dull brown or water-soaked con- 

 dition of the interveinal leaf tissue, simi- 

 lar to that pictured in fig. 16, developed 

 within 24 hours after treatment was 

 started, and was followed in another 24 

 hours by curling and wilting of the 

 leaves. Each seedling developed grayish 

 brown streaks similar to the streaks found 

 in current-season wood of trees naturally 

 affected with wetwood. These streaks 

 appeared in the last-formed wood, mainly 

 in the spring wood, and extended up the 

 stems from 8 to 24 inches above the 

 incisions and down the stems 4 to 10 inches 

 below the incisions. 



Greenhouse Tests on 2- Year-Old 

 Elms. — The toxicity of sap collected from 

 wetwood-affected elms in Hinsdale and of 

 the materials listed below was tested on 

 2-year-old greenhouse-grown seedlings of 

 American elm. The materials tested and 

 the number of trees that received each 

 material were as follows : ( 1 ) sterile dis- 

 tilled water, as check, 7 trees; (2) un- 

 sterilized distilled water, as check, 2 

 trees; (3) unsterilized sap from diseased 

 elms, 4 trees; (4) filtrate of sap from dis- 

 eased elms, 4 trees; (5) sap from diseased 

 elms, autoclaved, 4 trees; (6) filtrate 

 of sap from diseased elms, autoclaved, 8 

 trees; (7) precipitate of sap from diseased 

 elms — precipitate obtained by acidifying 

 the sap with sulfuric acid, filtering, then 

 resuspending the precipitate in alkalized 

 water — 2 trees; (8) sterile distilled water 

 in which healthy wood was soaked 1 

 year, 2 trees; (9) water acidified (pH 

 2.62) with hydrochloric acid, 4 trees; 

 (10) water alkalized (pH 9.5+) with 

 sodium hydroxide, 4 trees ; (11) suspen- 

 sion of living wetwood bacteria in sterile 

 distilled water, 1 tree; (12) filtrate of 

 nutrient broth staled by growth of the 

 wetwood organism, autoclaved, 4 trees ; 

 (13) filtrate of nutrient broth plus dex- 

 trose, staled by growth of the wetwood 



organism, autoclaved, 2 trees; (14) sus- 

 pension of ash from sap in distilled water 

 — suspension obtained by evaporating the 

 liquid and burning out the organic 

 materials — 2 trees; (15) filtrate of ash 

 suspension from (14), 2 trees. 



The stem of each tree to be treated was 

 fitted with a glass container similar to 

 that shown in fig. 24. The material to 

 be tested was supplied to this glass con- 

 tainer through the thistle tube. A piece 

 of small bore glass tubing, bent in a V 

 shape, was placed in the upper stopper 

 to serve as an air vent. After the container 

 had been filled, the upper stopper was lift- 

 ed sufficiently to permit insertion of a 

 sterile chisel, and an incision was made 

 in the stem beneath the surface of the 

 liquid ; this incision was made across the 

 stem at a downward slant through one- 

 third to one-half of the stem. The stopper 

 was then replaced and sufficient amounts 

 of material were added at intervals to keep 

 the level of the material above the incision 

 and to prevent air from getting into the 

 conductive tissues. The tests were run at 

 different times during the period from 

 July 30 to October 22, 1943, and all were 

 run in duplicate, except that for material 

 (11), suspension of living wetwood bac- 

 teria in sterile distilled water. Most tests 

 were terminated at the end of 5 days. 



The trees treated with the distilled 

 water, sterile distilled water, acidified 

 water, alkalized water, water in which 

 healthy wood was soaked, precipitate from 

 wetwood sap, water suspensions of living 

 wetwood bacteria, ash from wetwood sap, 

 and filtrate of ash from wetwood sap, 

 maintained their foliage and grew normal- 

 ly throughout the experiment. Data ob- 

 tained with the other materials, including 

 the check materials, are given in table 3. 



Trees treated with wetwood sap — un- 

 sterilized, autoclaved, filtered, and filtered 

 and autoclaved — with filtrate of staled 

 nutrient broth, and with filtrate of staled 

 nutrient broth plus dextrose, showed vary- 

 ing degrees of leaf discoloration, curl and 

 wilt. In general, filtrate of wetwood sap 

 caused the most rapid leaf discoloration, 

 curl and wilt. Bacteria in the wetwood sap 

 did not increase the amount or al¥ect the 

 type of wilt. Filtered sap was absorbed 

 in greater quantities than unfiltered sap. 

 In one test, sap that was filtered and auto- 

 claved, table 3, caused browning of inter- 



