23 



unnoticed. There is, however, a small amount of injury to fruits 

 and leaves, not due to parasites, which is to be ascribed to the heat 

 of the sun. On the leaves of unshaded coifee trees such injury is 

 represented by brown shriveled or sunken patches of cells, which in 

 their earliest stages are free from micro-organisms. Occasionally 

 such patches of injured cells form the center of yellowish areas. A 

 similar loss of chlorophyll on the upper side of the berries precedes 

 a premature ripening of the sun-exposed fruit. The berries that 

 ripen thus without being attacked by Cercospora are few in number. 

 That the injury in the case of the leaves is sun produced is indi- 

 cated by the absence of such " burned " tissue in the leaves of shaded 

 trees and the fact that those leaves with more nearly horizontal 

 or exposed positions are the ones affected. The injury by sunlight 

 is of interest in this connection as it favors infection of the fruits by 

 Cercospora. 



Since the existence of a close relationship between the distribution 

 of the disease and conditions as to shade would make possible a prac- 

 tical means of control, it was thought worth while to secure data 

 with regard to this. Accordingly samples were taken from each of 

 the gatherings made in two fields, one with fairly heavy shade, the 

 other exposed to the full sunlight. The quantity of berries examined 

 from each field varied from 132 to 199 liters per season, amounting to 

 from 15 to 20 per cent of the entire yield. The conditions as to soil 

 and slope were fairly uniform in each, so that the samples may be 

 taken as representing the quality of output fairly well. For two 

 years determinations were made of the proportion of Cercospora- 

 spotted berries, including spots of 1 millimeter in length or more. 

 It was found to vary according to the degree of maturity of the 

 samples examined, but reached for the last year 73 per cent for the 

 shaded and 70 per cent of such berries for the sun exposed. It was 

 concluded that, so far as the actual distribution of the disease goes, it 

 is not influenced largely by differences with regard to light. The 

 relative occurrence of the more troublesome or " sancocho " form of 

 the spots was quite different as, in the determinations made the fol- 

 lowing year, when there were taken only berries in which the spots 

 were sufficiently developed to be blackened and dried to the cascara, 

 it was found to be 16 per cent in the shaded and 27 in the unshaded 

 coffee. 



It is well known that there is considerable variation in the quality 

 of coffee, one of the characters of an inferior grade being the larger 

 proportion of blackened and shriveled grains. As it was thought the 

 Cercospora spot of the berry might be the cause of such grains, at 

 least indirectly, the spotted berries, used in the work already men- 

 tioned, were subjected to the usual process of preparing the grain. 

 In the case of those used in the earlier work, where even slightly 



