August ,1945 



Carter: Wetwood of Elms 



421 



Fig. 20. — The organism that causes wetwood 

 of elm produces cells that are short rods with 

 rounded ends and that occur singly or, rarely, 

 in pairs or chains. XI, 000. 



Fig. 21. — Cells of the wetwood organism 

 have peritrichiate flagella. X 1,500. 



ing, whitish cream and viscid, and is 

 accompanied by an odor of fermentation. 

 A culture of the organism growing on 

 cabbage infusion agar is shown in fig. 22. 

 Growth in stabs in potato dextrose agar 

 is abundant and is accompanied by the 

 liberation of gas. This gas produces 

 fissures and frequently forces a portion of 

 the agar up against the cotton plug or 

 beyond the mouth of the test tube. At 

 first the colonies are lens shaped to disk 

 shaped. The medium remains unchanged 

 in color. In shake cultures of potato dex- 

 trose agar covered with a mixture of 

 paraffin and vaseline, the organism 

 develops abundant growth through the 

 medium and produces sufficient gas within 

 20 hours to form fissures in the medium 

 and to start raising the paraffin-vaseline 

 seal. Growth on additional agars is as 

 follows : abundant on cabbage infusion ; 

 moderate on lima bean and wood decoc- 

 tion ;* scanty on bean pod, nutrient broth, 



*Wood decortion agar was made by adding 2 per 

 cent agar to distilled water in which normal elm wood 

 had been soaked for several days. 



corn meal, malt extract, prune, and plain 

 agar plus 1 per cent, 5 per cent and 10 

 per cent dextrose; hardly visible on wort 

 agar and on plain agar plus 20 per cent 

 dextrose. No visible growth develops on 

 2 per cent plain agar. Streak cultures on 

 potato plugs produce an abundant, fili- 

 form, glistening, dark gray growth that 

 darkens the potato tissue only slightly. 

 The texture of the potato tissue is not 

 visibly affected. Streaks on carrot plugs 

 produce scant growth, consisting of one to 

 a few beadlike glistening cream colonies. 

 Carrot tissue is not visibly affected. No 

 growth develops from streaks on apple 

 plugs. Milk is coagulated in 24 hours at 

 37 degrees C. and in 13 days at 24 degrees 

 C. There is a separation of acid curd with 

 the production of whey. The milk changes 

 to pH 4.1-5.1 by the end of 15 days. 

 Litmus and bromocresol purple are re- 

 duced. Milk is not peptonized. By Conn's 



Fig. 22. — Culture of the wetwood organism 

 growing on cabbage infusion agar. 



