1919) DISEA8E8 OF PLANTS. 451 



seena to be a Uttle richer than the diseased i"i ,s . whereas the diseased roots seem 

 to have somewhat more ash than the normal roots, silica was present In large 

 quantities when compared with the ash content of other plants, calcium showed 

 an Increased accumulation In both tops and roots of dl eased plants, and mag- 

 nesium was present In blighted plants in almost double the quantity round in 

 normal ones, a striking Feature of the Investigation was the bigh potassium 

 content of both normal and blighted plants. Phosphate absorption seemed In- 

 fluenced by the blight, and the iron content of blighted plants was less than that 

 of normal ones. 



The results obtained in the study of the oxidase activity resemble those ob- 

 tained in the study of other plant diseases, such as the mosaic of tobacco, curly 



t * « i » of sugar heels, ami leaf curl and curly dwarf of potatoes. The diseased ma- 

 terial shows a greater power to transfer atmospheric oxygen to certain aromatic 

 compounds than the healthy material. In all of the above-mentioned plant dis- 

 eases, which cause dwarfing of the plants affected, the capacity of the plant juice 

 to utilize atmospheric oxygen for tin- oxidation of certain chromogens is abnorm- 

 ally increased. How this increase in the catalytic activity of the cell sap is 

 brought about remains to be determined. 



It appears from the study of the effect of spinach blight on carbohydrate pro- 

 duction that the manufacture of carbohydrates is not inhibited by the disease, 

 although it may he retarded. The reducing sugars are practically absent from 

 the roots of all plants, while the tops of normal plants contain somewhat more 

 than the diseased. Both sucrose and starch are present in the leaves of dis- 

 eased plants in markedly greater quantity than in those of normal plants. They 

 are found in the roots of both healthy and diseased plants in approximately like 

 quantities. Determination of diastatic activity failed to bring out any marked 

 difference between healthy and diseased plants. The accumulation of carbo- 

 hydrates is considered due, not to a breaking down of digestion, hut to some 

 partial failure in the subsequent metabolic processes iu connection with which 

 carbohydrates are used. 



The accumulation of carbohydrates in the leaves of blighted plants is shown 

 not to be due to the inability of the diseased plants to make proteins. Although 

 carbohydrates were found in the tops of diseased plants in a somewhat smaller 

 percentage, calculated on the dry weight of the material, than in normal tops, 

 the proteins make up a larger proportion of the total nitrogen in the diseased 

 than in the healthy material. The proteins in the roots of blighted plants were 

 found to exceed those in the roots of healthy plants both with reference to the 

 dry weight and to the total nitrogen. Spinach blight is said to he physiologically 

 characterized by retarded growth and a lower moisture content This is con- 

 sidered to be due to the fact that the rapidly growing normal tissues are com- 

 paratively rich in water and poor in complex organic compounds, such as pro- 

 teins, etc. The lower percentage of total nitrogen and of acid amid nitrogen in 

 the diseased material is explained by the assumption that denitritication takes 

 place in these tissues, whereby a part of the nitrogen may he lost either as ele- 

 mentary nitrogen or in the form of ammonia. 



Brown blotch of the Kieffer pear. G. YV. Maktin (Phytopathology, S (IMS). 

 No. 5, pp. 234-239. flgt. 9). — The author describes a disease of Kieffer pears in 

 southern New Jersey which is locally known as brown blotch. While the 

 Kieffer pear is most seriously attacked, the disease is also found on other 

 varieties. 



The spots when small and scattered are usually circular and without well- 

 defined borders. As the season progresses, a number of the spots coalesce, 

 forming large, irregular patches or blotches and frequently covering one side 



