258 COLOCASIA BLIGHT. 



this species. It is, however, readily distinguished from Ph. Colocasice 

 by its regularly shaped and smaller sporangia. In the species on 

 Areca, as described by Coleman 1 , the antheridium arises, in some 

 cases at least, before the oogonium and the latter comes to lie 

 immediately above the antheridium, which is applied at its base. 

 His figures suggest an actual penetration of the antheridium by 

 the stalk of the oogonium (see especially PI. XVII, Fig. 9 and PI. 

 XVIII, Figs. 1 and 3). Rut the oospores are larger than in Ph. 

 Colocasice and the sporangia broader and borne on more branched 

 conidiophores, which form a dense felt on the nuts. The range of 

 hosts is also considerably wider. 



The only other species in which it appears likely that the 

 oogonial origin grows through the antheridium is Ph. infestans*. 

 Clinton's figures, especially PL XXXIX E and PI. XL, B, E, F 

 and I, are clearly capable of this interpretation. But the oospores 

 are larger than in Ph. Colocasice and the sporangia smaller and 

 borne on characteristically branched conidiophores and there is 

 no danger of confusing the two species. 



In none of the other species of Phytophthora which have been 

 described are marked relationships with Ph. Colocasice evident, 

 either in the sexual or asexual stages. The species is indeed one of 

 the most distinctive in the genus. 



VI. Treatment of the disease. 



Sawada reports an experiment to test the effect of Bordeaux 

 mixture in checking the disease. Half of an infected field was 

 sprayed with Bordeaux mixture to which soap had been added. 

 A month later the sprayed portion was found less infected than the 

 remainder, although there had been much rain and continued 

 gloomy weather. Before spraying all infected leaves were removed. 



Bordeaux mixture has considerable prospects of success, 

 owing to its proved efficacy in allied diseases. The sporangia are 



1 Coleman, L. C. Diseases of the Areca Palm, I, Koleroga. Bull. Dept, of Agric, 

 Mysore State, My col. Ser. No. 2, 1910, and Annates Mycologici, VIII, 1910, p. 591. 



2 Clinton, G. P. Oospores of Potato Blight. Conn. Exper. Sta. Report, 1909-10, p. 753. 



