472 RESEARCHES ON FUNGI 



leaf-spots which gave rise in succession to 0. flavida gemmifers and 

 sporophores. Similarly-treated isolated leaves of Plumbago capensis 

 developed leaf-spots which produced 0. flavida gemmifers only. 



Omphalia flavida is able to form leaf-spots on the leaves of species 

 belonging to the most diverse families of Flowering Plants and also on 

 the leaves of various Ferns. A list of the plants which 0. flavida is known 

 to attack has been given. 



The mycelium of Omphalia flavida, when newly obtained from gemmae 

 developed in the open on Coffee leaves, fruits vigorously. When the 

 mycelium is grown for several years on artificial media, it gradually 

 loses its fruiting power, but this can be restored in large measure by 

 passing the mycelium through living leaves. 



The formation of gemmifers on a mycelium of Omphalia flavida is 

 initiated by the stimulus of light and does not take place in complete 

 darkness. When an agar-plate in which 0. flavida is developing is ex- 

 posed to daylight on a laboratory table, the mycelium forms alternate 

 gemmiferous and non-gemmiferous zones corresponding with the diurnal 

 hours of daylight and darkness. 



The mycehum of Omphalia flavida, both in artificial cultures and in 

 leaf-spots, is luminous. This discovery has provided a means for diag- 

 nosing the American Coffee-leaf disease in the dark. At night, in a 

 Porto Rican Coffee plantation. Professor Albert Miiller was able to see 

 Coffee leaf-spots very clearly at a distance of 2-3 feet from the leaves 

 and less clearly, although distinctly, at a distance of 6-10 feet. 



Sderotium coffeicola, which causes the Sclerotium disease of the Coffee 

 plant in Dutch and British Guiana and in Trinidad, resembles Omphalia 

 flavida in attacking many different kinds of plants, including Coffee and 

 Ferns, and in producing gemmifers. An account of S. coffeicola, chiefly 

 based on Stahel's observations, has been given. 



A gemmifer of Sclerotium coffeicola consists of a little white knob-Hke 

 pedicel and of a detachable slender white needle-like gemma 1 •5-4-0 mm. 

 long and 0-05-0 • 1 mm. thick. The gemmae of S. coffeicola, Uke those of 

 Oynphalia flavida, are blown about by the wind, settle on host-leaves, 

 germinate there, and soon produce leaf-spots bearing new gemmifers. 



On fallen leaves and on Coffee berries the mycelium of Sclerotium 

 coffeicola produces sclerotia. On germinating, a sclerotium gives rise to 

 a feathery mycehum which bears gemmifers. Perfect fruit-bodies of the 

 fungus, so far as is known, are not produced. 



The mycelium of Sclerotium coffeicola is provided with clamp-con- 

 nexions, and this indicates that the fungus is a Basidiomycete. It is 

 possible, as Stahel has suggested, that the gemmifers of S. coffeicola, 

 which are rod-like in form and remind one of the fruit-bodies of certain 

 Clavariaceae, may be modified fruit-bodies of a Typhula. 



