as the stalks were coiieerned, but which had luid the fuugus on tlic 

 leaf-sheaths for some months. 



In contrast to these conditions, damage which can be attributed 

 to Melanconiiun has been observed, where weak varieties or over- 

 mature cane was involved. A variety known as D-625 has been 

 particularly noted suffering with typical rind disease, moth-borer or 

 other fungi not being present in sufficient amount to account for the 

 loss. It has also been a common experience to have fields, which 

 had been left over from one crop season to the next, either because it 

 was hoped the yield would be increased, or because it was impossible 

 to cut them before the grinding season closed, destroyed or rendered 

 worthless as far as the yield of sugar was concerned. Rayada, white 

 (Otaheite) and D-625 have been noted suffering in this manner. 



In addition to attacking over-mature cane, it is not uncommon 

 to be preceded by a weakening of the vitality of the cane through 

 the presence of the root disease, or some untoward soil condition. 

 This is especially true in old ratoons that are "running out," and 

 instances have been seen where such a state of affairs resulted in 

 total loss. 



In all cases in Porto Rico an infection with the rind fungus seems 

 to be preceded by a wealcening of the vitality of the cane through 

 some other unfavorable condition. Unfortunately these conditions 

 can not always be foreseen, and therefore rind disease must be con- 

 sidered as something of an obstacle to continuous good yields in spite 

 of its lack of a truly parasitic nature. In general, however, the 

 use of hardy varieties, not allowed to become over-mature and prop- 

 erly cultivated, will avoid any serious loss from this malady. 



The fungus will be further considered as a disease of cuttings 

 under that heading. 



Description. — The fungus produces a souring of tlie juice ;tnd 

 a soft wliite rot of the tissues, affected i,talks withering and drying 

 up. Fruiting pustules form in great numbers on thoroughly rotted 

 stiilks or on the base of leaf-sheaths, appearing first as small l)lack 

 slightly raised areas, several times longer than broad. The epiderm 

 covering these is soon ruptured permitting the black spore mass to 

 exude which, depending upon the moisture present, varies in shape 

 from a flattened mass to long thread-like processes. 



Melanconium sacchari Massee. 



Conidia produced in pycnidia (acervuli) formed imder the epi- 

 dermis, unicelluh.r, pale brown, cylindrical, straight or curved. 14- 

 15 X 3.5-4 mu. : -^ onidia extruded in long black eirrhi. 



195 



