200 



The Philippine Journal of Science 



is severely attacked by the rust and has been practically wiped 

 out in most regions. A few favorably situated districts, in high 

 altitudes, still produce Arabian coffee successfully. Owing to 

 Hemileia, Cojfea arabica Linn, is now of relatively slight impor- 

 tance in Java. Many plantations have been uprooted and re- 

 planted to C. robitsta or hybrid varieties. 



Causal organism. — The orange dust on the under surface of 



leaves is made up of the single- 

 celled irregular uredospores and 

 few single-celled teleutospores. 

 The uredospores are irregularly 

 obovate, bilateral, with short, 

 blunt spines on the dorsal sur- 

 face and with the ventral side 

 smooth. They are produced on 

 the leaf surface from stalks pro- 

 jecting through the stomata (fig. 

 14). The uredospores germi- 

 nate readily in water. Penetra- 

 tion takes place by way of the 

 stomata. The mycelium grows 

 in abundance in the air spaces 

 and in the intercellular spaces 

 of the leaf tissue. Teleuto- 

 spores are not produced in 

 abundance. They are small, 

 pale yellow, and smooth and 

 have a short, slender, hyaline 

 pedicel. They germinate often 

 on fallen leaves by the produc- 

 tion of a promycelium with 

 sporidia (fig. 14) . 



Control. — Control consists in 

 selecting resistant varieties and 

 in spraying with Bordeaux mix- 

 ture. As yet no resistant strain 

 of Coffea arabica Linn, has been 

 developed. In the Philippines, as shown by the College of Agri- 

 culture plantings, Coffea robusta is only slightly attacked and 

 Coffea arabica Linri. is severely attacked. The liberica varieties 

 need a special pulper, and the robusta coffee is of relatively poor 

 quality and commands a lower price. The arabica coffee, Coffea 

 arabiea Linn., is the most easily handled and is very productive; 



Hemileia vastatrix B. et Br. n, 

 infected coffee leaf, showing 

 mycelium in tissue and produc- 

 tion of uredospores some of 

 which were cut in sectionini? 

 <X 325) ; b, teleutospores (X 

 325) ; c. germinating teleuto- 

 spores, promycelia, and sporidia 

 (X 325) ; d, uredospores (X 

 325). 



