24 A. L. PlERSTORFF 



changed phases and began to form lysigenous cavities, both cell walls 

 and lamellae were broken down. 



The writer placed thin slices of unripe pear and apple fruits in 

 bouillon cultures of the fire-blight organism. Similar slices were placed 

 also in boiled and in fresh juices extracted from blighted pear fruits 

 as described in the discussion of toxins (page 14). In addition, pieces 

 of these infected fruits used for the toxin experiments were fixed in 

 chrom-acetic acid and sectioned in paraffin. In none of these tests 

 did a dissolution of the middle lamella occur prior to disintegration of 

 the entire tissue. In working with this material, the walls of the cells 

 were broken more frequently than they were split. This would indicate 

 that if any dissolution of the middle lamella occurs, it does so very 

 slowly. Also, the fact that blighted fruits and twigs are firm and are 

 not easily reduced to pulp by squeezing, lends support to this view. 

 From this it may be concluded that a lamella-dissolving enzyme or 

 pectosinase is secreted only in minute quantities, if at all, by B. amy- 

 lovorus under the conditions of the experiments. 



In testing for pectase and pectinase, pectin was prepared from Certo, 

 a commercial apple pectin, by coagulating with ethyl alcohol, filtering, 

 washing with cold water, redissolving in warm water, and recoagulating. 

 This process was repeated three times, and the pectin thus obtained was 

 dissolved in warm Uschinsky's solution from which the glycerin had 

 been omitted. The pectin was used at the rate of about 10 per cent 

 by volume. Tests for reducing sugars in this preparation proved to be 

 negative. All tubes thus prepared were incubated at 25° C. for two 

 days and tested for sterility. Nineteen tubes were divided into two lots, 

 lot 1 being inoculated with a culture of B. amylovorus and lot 2 serving 

 as a check. The tubes were examined daily for signs of coagulation. 

 No such signs were noted during a period of twelve days. At the end 

 of that time all tubes were tested for reducing sugars. If the enzyme 

 pectinase was formed, some of the soluble pectin should have been 

 hydrolyzed to the reducing sugar arabinose. No reducing sugars were 

 detected. If arabinose had been detected and no coagulation noted, 

 the test for pectase would not have been positive, as the enzyme pec- 

 tinase is able to hydrolyze soluble pectin and also the gel formed by 

 pectase. Conversely, pectase is without effect on pectic bodies previously 

 hydrolyzed by pectinase, according to Bourquelot and Herissey (1895). 



Since arabinose was not found in the cultures, nor any evidence of 

 coagulation detected, it must be inferred that under the conditions of 

 the tests neither pectase nor pectinase was produced. 



Cellulase 



Tests for the production of cellulase were made by placing pieces 

 of Reeve's Angel filter paper of known weight in Uschinsky's solution 



