400 



RESEARCHES ON FUNGI 



7 mm. diameter. As the leaf-spots become older, growth having 



stopped for any reason, 

 such as the advent of the 

 dry season, the diseased 

 tissue falls away, leaving 

 numerous circular open- 

 ings in the leaf. In other 

 leaf diseases the dead 

 tissue remains. 



" Sometimes the fun- 

 gus attacks young stems, 

 where it causes conspic- 

 uous scars and so weakens 

 the points affected that 

 they are easily broken by 

 the wind. The berries also 

 are attacked, a slight dis- 

 coloration of the grain 

 being frequently caused." 

 In Porto Rico the 

 disease is restricted to the 

 moister parts of the island, 

 but there the best coffee 

 is produced. The trees 

 with leaf-spots yield fewer 

 berries. " The injury to 

 the trees," says Fawcett, 

 " is not so much in the 

 actual amount of the leaf 

 tissue destroyed, although 

 this may amount to one- 

 fifth or even more of the 

 entire amount in the 

 worst cases, but in the 

 defoliations which take 

 place after a time. The 

 diseased leaves drop 



Fig. 200. — A Coffee leaf sliowing leaf-spots 

 caused by the mycelium of Omphalia flavida. 

 Each spot has arisen from a gemma, pre- 

 sumably blown on to the leaf by the wind 

 or splashed on by the rain. The spots, 

 apparently, have not yet produced any 

 gemmifers. They are luminous in the dark. 

 Photographed by G. L. Fawcett at the 

 Mayagiiez Experiment Station, Porto Rico. 

 About the natural size. 



