SCLEROTIUM COFFEICOLA 



451 



began to produce gemmifers 10-12 days after the leaves had been 

 inoculated with gemmae. A single leaf-spot may produce several 

 scores of gemmae. 



In dry weather the gemmae dry up, but they retain their vitality 

 for some time even in the dried condition. Stahel placed a number 

 of gemmae in a desiccator for varying periods of time and then tested 

 them for germination. He found that they retained their vitality 

 after two weeks in the desiccator, but not after three or four weeks 

 except for a single gemma which germinated weakly. 



Dry weather checks the progress of the Sclerotium disease ; 



Fig. 22j. — Sclerotium cqffeicola. Dead Coffee berries covered with sclerotia, lying 

 on the ground. Photographed by G. Stahel. Natural size. 



for, under these conditions, not only can new infections not take 

 place, but the leaf-spots already in existence cease to grow in size 

 and dry up. With the advent of dry weather, the leaf-tissues form 

 a callus around each spot which effectually prevents the spots from 

 increasing in size again when wet weather comes on. Stahel suggests 

 that the callus sets a limit to the growth of the mycelium by pre- 

 venting the toxic substance produced by the hyphae in the leaf-spot 

 from diffusing centrifugally. 



The sclerotia of Sclerotium coffeicola were discovered by Kuyper. 

 They develop in considerable numbers on the outside of infected 

 leaves and berries as these lie upon the ground under Coffee trees 



