WOUND DRESSINGS ON APPLE TREES 3 



phasized the differences in callus growth of the trees when trunk 

 wounds were made with an auger at different seasons of the year; 

 the healing was more rapid on wounds made in the spring than on 

 those made at any other season. Rose (11) also reported that callus 

 formation was better and injury less on wounds made in the spring 

 .than on those made at any other time. 



The work of Swarbrick (13), using sycamore, rhododendron, apple, 

 and plum, though not concerned 'directly with wound dressings, helps 

 to interpret the work reported herein. He showed that severing a 

 branch of about %-inch diameter, probably containing living cells 

 throughout its cross section during the growing season, May to 

 August, causes rapid disappearance of starch from the cut end, 

 followed by development in the vessel cells of a viscous substance, 

 which apparently blocks them. Wounds made in September and 

 October are only partly plugged and remain that way throughout 

 the winter, whereas those made from November to March, or in the 

 dormant season, show no plugging until growth activity begins in 

 May, at which time starch begins to disappear and gumlike sub- 

 stances develop. Blocking may be completed in 4 to 6 weeks from 

 the beginning of starch disappearance. Swarbrick's work indicates 

 that the accumulation of the resinous substances may result in differ- 

 ential penetration and killing by slightly toxic wound dressings ap- 

 plied at different seasons of the year. 



Cope and Spaeth (5) demonstrated that sodium arsenite was more 

 lethal when applied to tree wounds in the fall than when applied in 

 the spring. 



Tilford (14) reviewed the recent work on wound dressings and 

 reported experimental work on a number of different dressings on 

 forest trees. Liquid asphaltum accelerated healing on most of the 

 species treated. Other treatments in general produced healing com- 

 parable with or poorer than that on the checks. 



Walter and Mook (15) showed that the Ceratostomella that causes 

 a canker of the planetree may be carried by infected sawdust in 

 wound dressings. 



Many wound dressings containing a wide range of constituents 

 have been recommended by various workers. Very few of the recom- 

 mendations, however, appear to have been based on adequate exper- 

 imental evidence, and most of the dressings recommended have not 

 become generally used. 



DEVELOPMENT AND PRELIMINARY EVALUATION 

 OF WOUND DRESSINGS 



While attempts were being made to devise a wound dressing having 

 the desired properties, a large number of preparations reported in the 

 technical literature or by some plantsmen as having merit were 

 tested. Among the preparations tried were several types of grafting 

 wax, an asphalt-creosote mixture, paints containing metallic copper in 

 finely divided form, bordeaux dust in linseed oil, and Day's (7) mixture 

 of zinc chloride, alcohol, and hydrochloric acid. All these prepara- 

 tions were found to have some decided draw-back. 



In endeavoring to compound a wound dressing possessing the 

 desired properties, many different materials were used either alone 

 or in various combinations and in various proportions. Mixtures of 



