APPENDIX 289 



It appears that this aggressive parasite is known to 

 attack only four or five of the hundreds of varieties of 

 bananas. 



DISSEMINATION OF THE DISEASE 



As was noted in the first part of this article, owing to 

 the carelessness of man this disease has been widely 

 distributed by the planting of diseased suckers. If there 

 were no other method of spreading the disease, it might 

 be restricted to the progeny of originally diseased plants. 

 Unfortunately, however, Nature has provided for an almost 

 unlimited dissemination of the disease-causing organism 

 to new localities under the proper conditions in the follow- 

 ing ways: 



The fungus produces innumerable spores on both sur- 

 faces of the leaf-blade, on the leaf-stalk, or even on the 

 leaf -bases, apparently at any time of the year, the govern- 

 ing factors being the stage of the disease and the high 

 atmospheric humidity or abundant rainfall. 



These miscroscopic spores are easily dislodged, when 

 dry, by the wind, and carried in all directions on slight 

 currents of air, as they are extremely small and light. 

 How far these spores may be carried by the wind without 

 losing their vitality is not known, but theoretically a 

 distance of many miles is possible, so that it may be 

 assumed that the only practical limit in their dissemination 

 by wind agency is their desiccation death-point. 



In the tropical rains, which are so common in many 

 banana-producing countries, the water frequently accu- 

 mulates on the surface of the ground so rapidly that it is 

 not easily absorbed, but runs in sheets or streams for 

 considerable distances. There can be no doubt that this 

 affords a ready means for the dispersal of the spores for 

 short distances. 



It has been abundantly proved that the fungus may 

 remain alive in the soil in some form or other for long 

 periods of time. It has also been proved that the organism 

 is capable of growing in the soil. It is evident, therefore, 



