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Journal of Agricultural Research 
Vol. XXIV, No. 8 
minutes in water at a temperature of 54 to 55° C. As a practical method 
of control, treatment of rice seed in water for 10 minutes at 52° C., or for 
5 minutes at 54® after preliminary soaking for 24 hours at room tempera¬ 
ture, was recommended. 
The disinfection of rice seed by other methods, including possibly the 
hot air method devised by Atanasoff and Johnson (j) and treatment 
with various organic mercury compounds, presents a profitable field for 
further research. In this connection it may be mentioned, however, 
that the conidia of Helminthosporium oryzae appear to remain viable 
relatively long periods, the writer having germinated, in September, 
1921, spores from material collected in I^uisiana on October i, 1920, 
nearly 12 months earlier. (PI. 30, Cd, i, k.) As a result the fungus 
undoubtedly is able to survive from season to season on stubble, straw, 
and other refuse. Although the prevention of primary seedling infec¬ 
tion may reduce to some extent tlie number of secondary infections at 
later stages in the development of the plant, it can scarcely be expected 
to eliminate them altogether. As in the somewhat analogous disease of 
barley, wheat, and rye caused by H. sativum, generally approved agri¬ 
culture practices making for soil sanitation should prove of some value. 
In nature the fungus does not seem to have been found to attack 
plants other than rice, although on artificial inoculation Ocfemia (97) 
secured infection of 31 species of grasses belonging to 23 genera. Evi¬ 
dently this represents another instance in which the experimental host 
range is more an expression of the rigorous conditions attending the 
procedure followed than of significant parasitic relationships. 
Since the submission of this paper for publication, a valuable account 
of the Helminthosporium disease of rice has been published in English 
by Nisikado and Miyake (94a), not only incorporating the results of fiieir 
own comprehensive studies but also including suggestive allusions to a 
considerable volume of investigations, the reports of which have not 
hitherto become generally known among readers of the European lan¬ 
guages. Their full account of the morphology, pathogenicity, and cul¬ 
tural characters of the fungus, and their abxmdant illustrations, leave no 
doubt that the parasite found destructive in Japan and presumably in 
many other rice-growing countries of the Orient is altogether identical 
with the one discussed in the foregoing paragraphs. The lack of close 
agreement in measurements of conidia and conidiophores given by differ¬ 
ent authors would seem to be due in large measure to the variability of 
the fungus under different conditions of growth both in nature and more 
especially in artificial culture—^its behavior in this respect being again 
analogous to that of Helminthosporium sativum. In addition, the inclu¬ 
sion in the range of dimensions of the more extreme measurements by 
some authors, and their exclusion by others, have not made for any 
close correspondence. As a special instance, the range in diameter of 
the sporophore may be cited, some writers having included measure¬ 
ments of the inflated basal segments, or of the distended segments of the 
prostrate elements from whidh the sporophores arise, while others have 
excluded them. The latter course was followed in the present account, 
as it was believed that in a comparative treatment involving a number 
of species the figures thus obtained would have the greater significance. 
