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XX.—A DISEASE OF THE YAM. 
(Bagnisiopsis Dioscoreae.) 
EK. M. WaAxk®EFIELD. 
obviously a parasite, and the attack, though localised, is severe. 
Mr. Farquharson supplies the following notes :—‘‘ The speci- 
mens were collected early in November, 1917, in the Okigwi dis- 
trict of the Southern Provinces of Nigeria. So far I have only 
met the disease in this district. 
“Only the round-stemmed yams are attacked, never the alate- 
stemmed ‘water-yam’ types. So far as I was able to judge in 
with the stromata of the fungus, is very striking and unusual. 
did not see early stages of attack but the fungus is undoubtedly 
as soon as 
noticed. Though occurring more than sporadically, the trouble 
lying districts.” : : 
No previous record of such a disease of Dioscorea can be traced ; 
the yams as a rule appear to be remarkably free from serious insect 
and fungus pests. The fungus belongs to the order Dothideales, 
family Dothidengens, and is described below. It attacks the lateral 
