17 



distributed, but later appear in clusters beneath which are formed 

 wart-like outgrowths (sclerotia). The hair-like projections bear 

 minute spores which doubtless serve to distribute the fungus to some 

 extent. (PI. VIII, B.) This stage of the fungus (Dematophora) is 

 quite common, though produced less frequently on coffee than on 

 many other plants. (PI. Ill, fig. 2.) In the sclerotia are sometimes 

 formed other kinds of reproductive bodies that are characteristic of 

 the genus Rosellinia. (PI. VIII, A.) This seems quite rare, as the 

 writer has found it but twice, once on a wild shrub {Pijyer sp.) and 

 once on coffee. 



Among other plants than coffee which this fungus attacks is anamii 

 {Petiveria alliacea) , a weed quite common among the coffee. It was 

 observed to kill out a thickly growing area of this plant, a grass 

 (palmilla) taking its place. No other plant among the coffee has 

 been found to be injured except young guamas. Once when the fun- 

 gus escaped from pots of infected coffee plants it destroj^ed the 

 near-by growing ornamentals, Graftophyllum pictu7n, Panax j)lu- 

 rtiatum^ and Acalyph^ Tnosaica. It has been noticed once among the 

 trees and low growths at the edge of a clearing, attacking and killing 

 nearly all the plants with which it came in contact, among which, be- 

 sides the rose apple, were species of Miconia, Piper, and Palicourea, 

 all of shrubby habit. A Tradescantia, one of the common ground 

 plants in well-shaded coffee, covered the ground as soon as it was 

 cleared by the fungus. A fern {Adianfum sp.) seemed to be the 

 only plant able to resist its attacks except the large, thick-barked 

 guamas and mangoes. The fungus left a vegetation quite different 

 from that which it found, causing it to appear somewhat like that 

 of the clearings made for coffee. 



Although acting slowly, the losses to coffee produced by root dis- 

 eases are probably not exceeded by those from any other cause. The 

 injury is greater because the better trees suffer most, especially in 

 the case of the black root disease. The fungus causing this disease 

 is distributed throughout the coffee-growing regions of the island, 

 not being limited by climatic factors as are some other diseases. The 

 places where the trees have been killed are often left for a long time 

 before replanting, and after the trees are reestablished it is several 

 years before they bear fully. Just how long before the ground be- 

 comes fit for replanting without treating the soil with some fungicide 

 has not yet been determined, but this probably depends on the amount 

 of food material available to the fungus in the soil. In one case 

 noticed the trees replanted where the vegetation had been killed two 

 years previously have not shown, during a period of eighteen months, 

 any sign of the disease. 



Some experiments were made with the hope of finding an effective 

 way of controlling the disease. These have included ditching about 



