XXVI 
PLANT DISEASES 
WE did not discover any infectious diseases of the oil palm, Elaeis guineensis, 
or of the piassava palm, Raphia vinifera (Nos. 136, 333). Both of these palms 
are very common in Liberia and should be of great importance commercially. 
The coconut palm, Cocos nucifera, is not indigenous to West Africa, having 
been imported probably in the early years of exploration of the West Coast. 
Only one large grove of coconut trees was observed near Monrovia and more 
scattered trees were found in the vicinity of a number of towns along the sea- 
coast of Liberia. 
Coconut disease. On visiting the grove of coconut trees outside of Monrovia 
several of the trees were found to be diseased, and on examining microscopically 
minute sections of the trunks in which necrotic areas were present, large numbers 
of nematodes were found (No. 336). The idea then naturally suggested itself 
that the disease was identical with or allied to that known as “‘red ring” or ‘‘ Trini- 
dad root disease”’ in the West Indies and parts of Central America where we have 
previously studied the condition. However, the macroscopical lesions of the 
affection in the African coconut were not as well defined as those of the Central 
American disease in which a well-marked ring of necrosis is usually noted in the 
trunk several centimeters beneath the periphery. Nevertheless, the gross ap- 
pearance of the diseased trees was generally similar to that observed in ‘‘red ring”’ 
in that there was drooping and yellowing of the older fronds and beginning 
change in color in the younger ones. Dr. Linder, the botanist of the Expedition, 
who was also familiar with the red ring of South America, considered after 
examining the trees that the African affection was probably identical with the 
South American one (see page 522). 
One tree, illustrated in No. 335, was later chopped down and sections of the 
tree from near the top were made and studied. No distinct red ring of pathologi- 
cal tissue was here seen, but the cross sections of the trunk and petioles showed 
a pinkish tint. However, even in red ring, particularly in early infections, the 
characteristic ring of diseased red tissue, 3 to 5 em. from the cortex, often does not 
extend so high up the trunk. When fragments of this tissue taken from the 
trunk at least 15 to 20 feet above the surface of the ground were placed in water 
and observed under the microscope, very numerous motile nematodes were 
observed to have been set free. The note made at the time of the examination 
of different specimens of these nematodes with a higher power of the micro- 
scope states that some of the larvae were rhabditiform in structure, and rough 
drawings were made of them at the time. Portions of the tissue, together 
with the parasites, were preserved in formalin for further study. 
389 
