THE PESTS AND DISEASES OF THE CANE 165 



of inoculation experiments made in hot-houses in England with pure cultures 

 of the Colletotrichum, Howard obtained lesions characteristic of some phases 

 of the disease, with the absence, of course, of the black hyphae. In no case, 

 however, did he obtain disease lesions or growth with inoculations of the 

 Melanconium into healthy cane. When, however, the Melanconium was 

 inoculated into canes already attacked by the Colletotrichum , growth 

 followed with the appearance of the hyphse. Very shortly afterwards an 

 outbreak of rind disease occurred at the Georgetown Botanical Gardens. 

 Specimens of these canes were sent by Harrison and Jenman to Howard, 103 

 and on them he found one fungus only, which he identified as Diplodia 

 cacaoicola, known already as a parasite of the cacao tree. He showed that 

 this fungus is an actual parasite capable of producing all the outward 

 symptoms of rind disease when inoculated into healthy cane in pure 

 culture. 



In his publication on this subject he also brings forward evidence to show 

 that Darlucca mclasporum = Strumella sacchari = Coniothyrium melas- 

 porum = Diplodia cacaoicola, and that the fungus on the Mauritian canes 

 suffering from the Maladie de la Gomme was actually the Melanconium 

 fungus. 



More recently the perfect stage of the Diplodia has been obtained by 

 Bancroft and named by him Thyridaria tarda 91 



On the other hand Johnston considers the Darlucca, Strumella and 

 Coniothyrium as the same as the Melanconium. 



Butler has also studied the D. cacaoicola in India as the cause of dry 

 rot of the sugar cane. He regards the organism there as only mildly 

 parasitic. 



A third rind fungus, Cytospora sacchari 12 has been observed by Butlei 

 as parasitic on the cane in India, and later was found to be present also 

 in the West Indies. 



Two other fungi, Melanconium saccharinum 97 and Nectria laurentiana 96 

 are known to occur on the rind. Finally it may be mentioned that the 

 macroscopic appearance of canes affected by Gnomonia iliau sometimes 

 somewhat simulates that of rind disease. 



Whether the Melanconium fungus is to be regarded as strictly sapro- 

 phytic still remains in doubt. Cobb 81 in Australia took the view expressed 

 in^the following quotation : 



" I believe that it is true in most cases, if not in ah, this fungus requires the 

 cane to be injured. Perhaps the frost so injuies the arrow of the cane as to cause 

 it to decay or die ; perhaps a borer makes its way into the cane, and thus breaks 

 the rind ; or again perhaps the wind twists the stalk and cracks it, or the cane 

 gets injured in any of the numerous possible ways ; then the fungus stands ever 

 ready to take advantage of the accident, and in a few weeks' time makes such 



inroads as to send the whole cane well on the way to decay The amount 



of damage done by spume is very difficult to estimate, There is no doubt that 

 through its agency much cane, which otherwise would be saleable, is soon rendered 

 worthless." 



Afterwards, in Hawaii, he considered the organisms as distinctly parasitic, 

 and to it he ascribed the frequent non-germination of cuttings. Lewton- 

 Brain 104 also treats the fungus as parasitic, and indicates that although the 

 hard outer rind is protective the fungus may enter through a wound, and in 

 the case of a susceptible variety may bring about the death of the stalk. 



