19:?L\ SUGAR CINE FESTS AND DISEASPJS. 117 



This remirkable coudition is very coui^picuous and its presGnce on 

 some of our vai'ieties led us at first to doubt whether mosaic disease 

 was the cjiuse. 



After a longer experience we find tliat there is no doubt as to its 

 occurrence only in plants wliich show typical signs of mosaic disease 

 in the younger leaves. Mr. Brandes of the U.S. Bureau of Plant 

 Industry writes that they have observed it in a smallnumber of varieties 

 susceptible to mosaic disease in Louisiana. 



Mr. Nowell has examined some of these leaves and found no trace 

 of any fungus disease and the only alternative to its being a normal 

 stage of mosaic in these \-arieties is that it miglit be due to some weakl ;/ 

 parasitic bacterium whicli is unable to infect healthy leaves. It is 

 hoped that this point will be investigated in the coming year. The 

 condition is particularly conspicuous in the canes D. 3956 and D. 6450. 



Tlie cankering of the cane- itself, I.e. the development of typically 

 longitudinal white stripes exteixling from the nodes of the cane, followed 

 in bad cases by shrinking of the internodes, is only found in canes that 

 have been infected for some considerable time. It can however develop 

 conspicuously in the first year of infection. It was mentioned in my 

 previous report that it was particularly distinct in B. 16536 and B. 6450, 

 and has recently been found well developed on " Congo Red." 

 Few observations on this condition have been made as all infected canes 

 found have been destroyed as soon as possible after infection.. 



The visible effect of mosaic disease on the health and growth of the 

 pliint varies considerably in different varieties. It is most distinct 

 where the plants have been grown from infected cuttings. In one bed 

 of T. 67 the infected plants, about six months old, were indistinguishable 

 in size from the healthy ones, while in an adjacent bed of D. 109 the 

 infected plants were without exception small and stunted and less than 

 one-quarter of the average size of the healthy plants. 



In an experiment plot of diseased and healthy plants of a number of 

 varieties, the following differences were observed after four months 

 growth : — 



Effect of disease. 



..Diseased distinctly smaller than healthy. 



..Diseased distinctly smaller than liealthy. 



..Very slight difference. 



..Diseased average about 25 per cent, smaller than 



healthy. 

 ..Very slight difference. 

 ...Diseased distinctly smaller than healthy. 

 ...Diseased noticeably smaller than healthy. 

 ...Diseased slightly smaller than healthy. 

 ...Diseased at least 50 per cent, smaller than healthy. 

 ...Diseased slightly smaller than healthy. 

 Badilia ...Diseased very slightly smaller than healthy. 

 In the same plot the relative death rate of diseased and healthy 

 canes was observed. It was found that thirteen out of 87 diseased 



