426 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 4 



the stems were cut, and the presence or 

 absence of bacteria in the solutions tested. 

 The amount of solution (0.2 ml.) from 

 the 24-hour culture of isolate 41—173 

 taken in by the shoots may have been 

 limited in part by mechanical plugging of 

 vessels by bacteria. However, the tomato 

 shoot in this solution did not wilt, even 

 though the elm shoot in the same test 

 tube wilted in 1.5 hours. Filterable and 

 thermostable toxins were not produced in 

 nutrient broth plus dextrose by isolate 41— 

 173. The hydrogen ion concentrations of 

 the solutions used, which ranged from pH 

 4.65 to 8.14, appeared to have no effect 

 on the elm and tomato shoots. 



Field Tests on 2- Year-Old Elms. 

 — In this experiment, six 2-year-old potted 

 seedlings of American elm were connected 

 by rubber and glass tubing to six large 

 wetwood-af¥ected elms in Hinsdale to test 

 the toxic effect, on seedlings, of sap from 

 wetwood trees. Two additional potted 

 seedlings were maintained as check trees. 

 Four of the six large elms had wilted in 

 previous years. Sap from the large trees 

 was carried to the seedlings through 

 rubber tubes and improvised glass con- 

 tainers. A glass tube, 29 mm. in diameter, 

 about 3.5 — l-.O inches long, was placed 

 around the stem of each seedling to be 

 treated, care being taken not to injure the 

 foliage as the tube was slipped down over 

 the seedling. Rubber stoppers, with holes 

 cut to fit, and split to the outside, were 

 fitted around the stem and inserted in each 

 end of the glass tube. The upper stopper 

 had two additional holes into which two 

 glass tubes were inserted. One of these 

 tubes, plugged with sterile cotton, served 

 as a vent. To the other tube was attached 

 rubber tubing which extended to a piece 

 of one-half inch threaded pipe fitted into 

 a hole bored in the diseased tree trunk. 

 The whole apparatus was arranged in 

 such a way that sap from the wetwood- 

 affected heartwood of the large tree 

 flowed into the glass container around the 

 stem of the seedling. 



On each of four of the eight seedlings, 

 a transverse incision was made by remov- 

 ing a V-shaped piece of stem. Three of 

 these seedlings were attached by tubes, as 

 described above, to elms affected with 

 wetwood. The fourth, used as a check, was 

 not attached to a tree; its glass container 

 was filled with sterile distilled water. 



Each of three of the remaining seed- 

 lings was attached, as described above, 

 to an elm affected with wetwood and, 

 when the glass container was full of 

 sap, a transverse incision was made at a 

 downward slant in the stem beneath the 

 surface of the liquid. A similar incision 

 was made in the stem of the single remain- 

 ing seedling, whose glass container was 

 filled with sterile distilled water. 



The two seedlings which received 

 water grew normally throughout the 

 experiment. The three seedlings given sap 

 through V-shaped incisions did not wilt. 



Fig. 24. — Apparatus used in supplying wet- 

 wood sap and other materials to potted elms. 



