478 



CITRUS FRUITS AND THEIR CULTURE. 



The fuiigus is a saprophyte, 

 and is dependent upon this honey- 

 dew for its sustenance. The in- 

 sects already referred to are gre- 

 garious in their habits. Conse- 

 quently, the honey-dew accumu- 

 lates in considerable quantities 

 on various parts of the plant, 

 and in this substance the fungus 

 lives. The black covering is com- 

 posed of its vegetative threads. 

 A number of different kinds of re- 

 productive bodies are produced, 

 and, through the agency of the 

 wind, are carried about from tree 

 to tree. Wherever suitable food 

 material is found, there the fun- 

 gus develops. 



Fig. 104. Sooty-mold. A, Myce 



Hum. B, Conidiophores. C, Con 



idia or spores. (Enlarged.) 



It is when it follows the at- 

 tacks of the white fly, Aleyrodes 

 citri, or allied insects occurring in enormous numbers on 

 citrus trees, that it does the most damage. The white 

 fly spends a great portion of its life on the under sides 

 of the leaves. The honey-dew exuded by it falls upon 

 the upper sides of the leaves beneath and upon the twigs 

 and the stem ends of the fruit. In this honey-dew the 

 fungus grows and soon covers the trees with a thick, 

 black, sooty covering, so that they appear from a distance 

 as though covered with a liberal application of stove- 

 black. 



Sunlight is necessary to the leaves of a tree, that they 

 may carry out their work in the plant's economy. The 



