88 BACTERIA IN RELATION TO PLANT DISEASES. 



Comparative studies were made by Harding and Morse* of forty of these forty-five strains, and 

 three others, and their conclusion is that these forty strains probably constitute only one somewhat 

 variable species. 



Both living cultures and the alcoholic precipitates were used by Jones in these comparative 

 studies. The experiments proved that these forty-five strains secreted the same middle-lamella- 

 dissolving enzym as B. carotovorus, and that, moreover, in these strains also complete solution of the 

 cellulose and diastasic action are lacking. 



After reviewing the literature the author states that he is convinced Green is right in his con- 

 clusion that the cytolytic enzyms fall into two natural groups, the one acting upon the pectic, and 

 the other upon the cellulose elements of the cell-wall. Further knowledge regarding the chemical 

 composition of the cell-wall will doubtless lead to a further subdividion of the enzyms acting upon 

 it. At present we recognize in the cell-walls of the less modified plant tissues the following: i. True 

 celluloses. 2. Hemicelluloses. 3. Pectic compounds. In the more modified tissues there are com- 

 pound celluloses, ligno-cellulose, etc. 



There is evidence that there are enzyms which act upon the true celluloses but the cytolytic 

 enzyms which have been studied in detail act only upon the hemicelluloses and pectic compounds. 

 Believing these cytolytic enzyms to be as clearly separable into two groups as the elements on which 

 they act, the author thinks it advisable that a distinct name be given to each of these two groups 

 of enzyms. 



The enzym of B. carotovorus and of related soft-rot bacteria acts upon the pectic compounds, 

 but not upon the hemicelluloses. Usually heretofore such an enzym has been termed "cytase." 



The author believes, however, that a more distinctive term should be applied to this class of 

 enzyms, and inasmuch as the logical one of "pectase" has already been applied to Fremy's clotting 

 enzym, he favors the name pcctinasc, which was suggested by Bourquelot and Herissey. This term 

 was originally applied to the enzym which hydrolyzes pectose, but it was found later that this same 

 extract hydrolyzes the coagulum, or pectic clot, and if, as seems probable to the author, this latter 

 action is due to the same enzym as the former, this name must be accepted for the enzym under 

 discussion. Jones gives the following definition of " pectinase:" 



"Broadly defined, then, pcctinasc is capable of hydrolvzing pectose when in solution so that it 

 will no longer yield a clot under the influence of pectase, and also of hydrolyzing the pectic coagulum 

 and the pectic elements in the cell-wall, viz., the middle lamella and parts of the inner lamella? of 

 certain tissues." 



Bourquelot and Herissey did not state that their enzym does not act on hemicellulose; in fact, 

 hemicellulose is acted upon by barley malt solution with which their work was done. Taka-diastase 

 acts predominantly on hemicellulose, although action on the pectic compound occurs also. Either 

 two enzyms are present in taka-diastase or there is only one which is allied to "pectinase" but differs 

 from it in its ability to act on hemicellulose. Newcombe's results strongly favor the first and exclude 

 the second of these two possible explanations. 



Believing that two enzyms are present in taka-diastase, barley malt, etc., pectinase and an 

 enzym acting upon hemicellulose Jones suggests for the latter the name "hemicellulase." Thus 

 the name "cellulase" could be used to include all cellulose enzyms, or, as the author believes preferable, 

 reserved for enzyms acting upon cellulose proper. 



"Their studies did not include the following: Pember's R., Pseudomonas iridis, nor the New York organisms O. 

 II 6 c, O.i II 6 a, and the bacillus from Amorphophallus. 



