DISEASES OF SUGAR CANE 303 



On resistant varieties the fungus appears to be able to make 

 headway only in injured or otherwise weakened stalks. Insect 

 attacks, defective soil aeration, and premature ripening as a 

 result of dry weather decrease resistance. 



Control. 



Butler has worked out a successful system of control based 

 on the information as to infection noted above. Starting with 

 healthy stock, a thorough inspection is made each year of the 

 cuttings prepared for planting. All which show reddening at 

 the ends are discarded. A previous selection of healthy-looking 

 stools as the source of the sets diminishes the trouble and in- 

 creases the efficiency of the process. By eliminating in this way 

 the results of casual infections it is found that in ordinary cir- 

 cumstances the condition of the stock can be maintained. 



The Rind Fungus. 



Although Melanconium Sacchari (Cke.) Mass. was not the 

 originating cause of the epidemic of " rind disease," it certainly 

 provided the feature which led to the use of that name, and it 

 seems appropriate to retain the adjective in speaking of this fun- 

 gus. As Strwnella Sacchari it was described by M. C. Cooke from 

 material received from Queensland in 1890. As already related 

 its uniform occurrence on diseased canes received at Kew from 

 the West Indies led to its being regarded as the cause of the 

 failure of the Bourbon cane. It is still everywhere abundant in 

 the West Indian cane-fields, occurring on probably every sickly, 

 damaged, or dead cane. It appears on the soundest and healthiest 

 canes with great regularity if these are cut and laid aside either 

 indoors or out. It occurs in a similar way in Louisiana, in 

 Mauritius, Java, and the Hawaiian Islands. In India it appears 

 to be very rarel}'' met with. 



Conditions of Occurrence. 



The germ-tubes of the fungus are unable to penetrate the 

 unbroken rind, but gain access through borer holes, torn leaf 

 scars, cracks, or wounds of any other description. In healthy 

 growing canes the invasion seems to be definitely restricted to 

 the tissue affected by the wound. In over-ripe canes, however, 

 it is able to spread, and when they have stood long in the fields 

 an ever increasing proportion of them become infested with 

 this fungus without there being any apparent reason for sus- 

 pecting preparation by any earlier organism. The view now 

 generally held regarding the degree of parasitism of which 

 this fungus is capable is that it is only able to occupy tissue 

 which has undergone seme degenerative change, due either to a 

 wound, to the actioi? o a previous organism, to senescence, or to 



