26 



ence of grasses which always come in where shade is lacking. The 

 trees in these places are slender, with few branches and but little 

 foliage. The leaves of the branches on which berries set fall when 

 these are half grown and the branches begin to die back at the tips. 

 Where the blackening extends rapidly, killing the bark and pedicels, 

 the " granos vanos " result. The trees, which are dependent on new 

 branches for leaves and berries, are able to form but few of these. 

 A product of inferior quality results, owing to the action of certain 

 diseases of the fruits and grain, thus increasing the loss caused by 

 lessened yield. 



STUDIES OF THE SPOT FUNGTJS. 



It is desired to include at this place something of the technical part 

 of the study. In attempting to determine definitely the nature of 

 the organism producing the spots, the earliest stages of the spots 

 were studied. The berries with such spots were first sterilized and 

 then introduced into the medium, or the spot itself was cut out and 

 introduced into the medium, using the usual precautions. When the 

 sterilization had consisted in washing the berries for three minutes 

 in 90 per cent alcohol, then placing them in 4 per cent formalin for 

 three minutes, and finally w^ashing in sterilized water, the spotted 

 berries usually gave, in addition to a sterile gray fungus, a Gloeo- 

 sporium, while the check unspotted berries similarly sterilized often 

 gave a Gloeosporium. With less severe sterilization a Fusarium Avas 

 often obtained in addition to the above. Later work, with more 

 thorough sterilization, gave only the sterile fungus from the spots. 

 Both the Fusarium and the Gloeosporium were tested in inoculations, 

 but without positive results. The sterile fungus was used in inocu- 

 lations, with the results that typical spots were produced on which 

 Cercospora spores later developed. In the checks small pieces of 

 sterile absorbent cotton of about the same size as the pieces of 

 mycelium were introduced into small wounds, the purpose being 

 roughly to duplicate the conditions of the inoculation. No infection 

 resulted in the case of those checks, although the chances of such 

 mfection from natural sources existed. No attempt to sterilize the 

 berries on the trees before this inoculation was made, and the results 

 showed it to be unnecessary. From the spots resulting from the 

 inoculation the usual gray sterile fungus was reisolated. 



No spores of Cercospora were borne on the mycelium in artificial 

 culture. However, on some of the mycelium placed on the berries 

 but slightly introduced into the wound, abundant spores of Cerco- 

 spora were in one instance produced. The material used in the inocu- 

 lations of the following season was obtained from spores developing 

 on typical spots of the berries. The spores, because of their com- 

 paratively large size, are easily isolated from drop cultures. The 



