16 



black type of the disease, Avhich is perhaps the more common, is the 

 one referred to in this bulletin unless otherwise stated, as it has been 

 possible to study it more thoroughly (PL III, fig. 1). 



The disease having made its appearance in one or more trees ex- 

 tends to the surrounding coffee trees. Its advance, which is very 

 slow, is marked by the dying or dead coffee trees at the edge of the 

 diseased area. In one case, when it was possible to determine the rate 

 of progress fairly readily because of the disease attacking the thick 

 herl3aceous undergrowth, it covered from 10 to 12 feet in one year. 

 Usually the growth is less rapid than in this instance. The only 

 things which retard or stop its progress seem to be excessively dry or 

 excessively wet soils, natural barriers, such as brooks, and the scarcity 

 of food material (decajang vegetation) in the soil. The conditions 

 favoring its growth are those provided by moist shaded soils, which 

 usually offer an abundance of food material. Unfortunately, these con- 

 ditions are also those favorable to the coffee tree, so that the disease 

 often does most harm among the best trees, the sun-exposed dry slopes 

 of poor coffee plantations remaining quite free from the trouble. In 

 more than one instance it has seemed to start with the decay of a 

 stump or tree trunk. As the fungus is laiown to live on dead vege- 

 table matter, it is probable that these stumps furnish such abundance 

 of food material that it becomes strong enough to attack living plants, 

 whereas ordinarily it merely makes use of the usual decaying mate- 

 rial covering the soil in well-shaded places. 



In the black form of the disease that part of the trunk just above 

 the surface of the ground becomes covered for a few inches with a 

 thin brown closely adhering coating of the fungus mycelium soon 

 after being attacked. On the roots and parts of the trunk below 

 the surface the mycelium is gathered more into strands of a brown 

 color which later becomes black. Below the thin outer bark the 

 threads form a nearly solid layer, thickly grow^n together. From 

 this there extends into the bark and wood root-like branches less than 

 1 millimeter thick. On cutting away the bark and wood these ap- 

 pear as small black dots and lines, according to the angle at which 

 they are cut. These form one of the most characteristic features of 

 the disease. In trees recently killed the fungus will be found to have 

 passed but little deeper than the inner bark, although in old stumps 

 it may penetrate 2 or 3 centimeters. The attack is usually near the 

 surface of the ground, involving the trunk at the surface and some- 

 times also the uppermost roots. It later advances downward for a 

 few inches, but the deeper roots usually remain uninjured. Occa- 

 sionally on that part of the fungus growth near the base of the trunk 

 there are formed numerous small hair-like projections 1 to 3 milli- 

 meters long. These are light colored at the tips, close together, and 

 have a somewhat brush-like appearance. At first they are evenly 



