O92 REPORT OF THE HARVARD AFRICAN EXPEDITION 
In typical red ring which we have observed in Spanish Honduras and 
Panama, the diseased trees usually show a progressive yellowing and brown- 
ing of the leaves, commencing at the tips, the nuts being shed slightly in ad- 
vance of the discoloration of the leaves and in a green condition. This may 
be the first external evidence of the infection. On section the stem shows a 
well-marked, complete ring of reddish-brown tissue, usually from 2.5 to 4 em. in 
width and about 2.5 to 5 em. from the periphery of the stalk. The diseased tissue 
may extend up the stem several feet and then become broken into longitudinal 
streaks and irregular small patches. The leaf stalks may also show these same 
pathological conditions. The roots become affected in the cortex, first under- 
going yellowish or pinkish discoloration and softening, later becoming brownish- 
red and sometimes dry and flaky. 
Cobb, in 1919, discovered a nematode Aphelenchus cocophilus to which 
he ascribed the cause of this red ring. In our studies in Central America ' we 
confirmed the presence of this parasite which occurs abundantly in the roots 
in the areas where the tissues are softened. The parasite undergoes its com- 
plete life-cycle in the diseased tissues where the eggs are also deposited. The 
larvae which hatch from the eggs then invade the more healthy tissue. Lar- 
vae were found not only in the roots but also in different parts of the trunk 
and throughout the diseased tissues. While the habits of these nematodes 
outside the host plant have not been thoroughly studied, it seems reasonable 
to suppose that on the falling of diseased leaves or trunks the nematodes would 
ultimately find their way to the surface of the soil and subjacent layers, and 
that infection of the young plants might take place by the migration of the 
nematodes from the soil to the new plant. It has been shown that the nematode 
will live for a considerable time in the soil about an infected palm. 
Experiments upon the Central American infection were conducted by 
Nowell ? and Cobb ? in which portions of diseased tissue containing these nema- 
todes were inserted into healthy palms. Typical disease conditions were pro- 
duced in this manner. 
More recently Zetek* has suggested that the termite, Coptotermes niger 
(Snyder), may be a mechanical carrier of this nematode from the old host to 
the new plant, he having demonstrated nematodes clinging to the bodies of 
the termites which were living in a coconut palm infected with red ring. How- 
ever, while infection may sometimes be transmitted through the agency of 
termites, they do not serve as the agent of transmissal in all cases since in many 
coconut palms infected with red ring no infestation with termites is present. 
Further examination after our return to the United States, of the nematodes 
which we had obtained from the coconut disease of Africa, revealed the fact 
that they did not belong to the genus Aphelenchus. The photomicrograph of a 
male specimen (No. 336), conclusively demonstrates this fact. The material 
! Strong: “International Conference on Health Problems in Tropical America,’ United Fruit Co. 
(1924), p. 917. 
2 Nowell: West Indian Bull. (1919), XVII, 189. 
3 Cobb: West Indian Bull. (1919), XVII, 203. 
4 Zetek: U.S. Dep. Agriculture Bull. (1924), No. 1232. 
