268 



U. SUZUKI. 



the normal growth of the shoots will be seriously impaired and 

 starvation must set in ; the leaves remain small and their tissues 

 develop only partly. For the same reason, the disease must be 

 induced by the frequent plucking- of the leaves. This view was 

 comfirmed by numerous observations and no doubt could further 

 be entertained about the correctness of my inferences. But there 

 remain still many points to be investigated, in regard to the 

 various pathological phenomena, accompanying the deficiency 

 of reserve materials, and also in regard to other secondary 

 causes which accelerate the disease. Finally methods of check- 

 ing or preventing the disease should be found. The following 

 investigations were carried out with the intention to throw more 

 light upon the pathology of the disease. 



OXIDIZING ENZYMES. 



The wide distribution of oxidizing enzymes in the vegetable 

 kingdom has recently attracted the notice of many plant physio- 

 logists and various investigations have been made upon the 

 nature and the physiological actions of these interesting sub- 

 stances. Albert F. Woods 1 has propounded the view that 

 the change of chlorophyll in the autumnal yellowing of leaves 

 is chiefly due to their action, a view which seems to agree well 

 with the fact that the oxidizing enzymes are abunduntly produced 

 in autumn when the activity of the cells in the leaves decreases. 

 If such leaves are ground in - a mortar with addition of some 

 water, the green colour will soon be changed to reddish brown, 

 while generally the green of the leaves in full vigour is but 

 slowly changed. Woods has also made very interesting obser- 

 vations on the influence of the oxidizing enzymes upon various 

 diseases of plants. Thus he found that the plants diseased 

 either by some physiological causes or by the attacks of insects 

 and fungi or by some mechanical disturbances, produce always 

 an abnormal quantity of oxidizing enzymes. He made especially 

 careful examinations of albinism or variegation of many plants, 

 especially of the so-called "Mosaic disease" of tobacco : In the 

 light green parts of the diseased leaves, always much of the 

 oxidizing enzymes has been found, sometimes even five or six 

 times more than in the normal leaves. Further those discolored 



i Centr.-Bltt. fur Bakt. II. Abt. V. Band 1899 No. 22. 



