94 Journal of Agricultural Research voi. vi, no. a 



decomposition of neucleoproteins. On the contrary, the phosphorus of 

 fraction 3 shows an increase of 30 per cent, that of fraction 2 an increase 

 of 20 per cent, and that of fraction i a decrease of about 7 per cent. 

 The increase in water-soluble phosphorus in fraction 2 indicates that 

 decomposition processes are taking place, but the concomitant increase 

 in phosphorus content in fraction 3 shows that such decomposition is 

 accompanied by actual synthetic processes involving the use of phos- 

 phorus. 



No difference appears between the two tissues in amounts of ash as 

 shown in fraction 3. The ashing of fractions i and 2 gave unsatisfactory 

 results and for this reason the figures are withheld. 



It is evident from the foregoing statement of results that the significant 

 changes brought about in diseased tissues concern carbohydrate and 

 nitrogenous constituents. The concurrent disappearance of mono-, di-, 

 and poly-saccharids from diseased tissues indicates that all the sucroclas- 

 tic enzyms previously shown to be formed by the organisms in pure 

 cultures are active in the host tissues and that the reducing sugars 

 formed are utilized by the organisms as sources of energy. The results 

 with nitrogen indicate that there is not an accumulation of the products 

 of protein decomposition but that the destructive transformation of 

 protein is accompanied pari passu by a utilization of the decomposition 

 products in the anabolic processes of the organisms. 



AGENCIES CONCERNED IN DISSEMINATION OF CITRUS CANKER 



Definite experimental data are wanting on the agencies by which 

 Citrus canker is spread. If we judge, however, from field observations 

 and from a knowledge of other bacterial plant diseases, it is evident that 

 rain and dew are important factors in carrying the disease to unaffected 

 leaves, twigs, and fruits of trees in which the diesase is already present. 

 Man himself is a very important agent in effecting the distribution of 

 canker from diseased trees to healthy trees near by. When in the cul- 

 tural operations of budding, cultivation, picking, etc., he comes in con- 

 tact with diseased trees and soon afterwards touches healthy ones, infec- 

 tion may result. The chances of infection are greatly increased if he 

 comes in contact with newly formed cankers on the diseased trees, and if 

 a film of moisture is present on the adjacent healthy trees which he may 

 touch. The most plausible explanation of the introduction of Citrus 

 canker into two groves which have come under the writer's observation 

 is through the agency of man. The owners had visited groves in which 

 canker occurred in order to acquaint themselves with the appearance of 

 the disease. On returning home they examined certain of the trees in 

 their own groves and these trees soon afterward developed canker lesions. 

 Stirling (2) reports the transmission of the disease through handhng dis- 

 eased leaves prior to touching healthy ones. It is highly probable that 



