SUMMARY. 
1. The symptoms of the “lyer” disease of maize in Java can be divided 
into three different types. 
First type: the attacked plants remain small with narrow leaves; they 
are yellow or greenish yellow (Plate 1). Often plants of this type lay down 
in consequense of poorly developed rootsystem (fig. 1). 
Second type: the plants are of normal development with yellow striped 
leaves, emerging from a common base in the basal part of the leaf (Plate 
IH, II). 
Third type: the diseased plants are of normal appearance, only the 
basal leaves shown narrow, sharply defined stripes, yellow or brown in 
colour. The stripes very seldom anastomose at their basal part (Plate IV, V). 
2. The “lyer” disease in Java is caused by Sclerospora javanica nom. 
nov. (Syn. Peronospora Maydis RAciBorskI1 1897, P. Maydis RUTGERS 1916, 
Scl. Maydis BUTLER 1913 pro parte). Only a conidial fructification has till 
now been found. The resting spores, described by RACIBORSKI, are spores 
of a Paramoecium, the chlamydospores and oospores which RUTGERS 
supposed to belong to this species have been proved to be resting spores 
of a Pythium. 
3. The corn-Sclerospora from British India, described by BUTLER, is 
not identical with the javanese one on corn. It is to be named Sclerospora 
Maydis BurteRr. This species also occurs in the Philippines. 
4. The conidia of Sclerospora javanica germinate with a germtube 
which penetrates the leaf through one of the stomata. The infection power 
of the conidia is retained about one day if laying exposed on the leaf; in 
or on the ground after 4 days the infection power seems to be lost. 
The conidia are disseminated by the aid of the wind. Studies in the field 
have proved the presence of conidia in the air and have shown that the 
conidia are able to travel over a distance of more than two kilometer 
without losing their infection power. The maximum distance of dissemination 
remains yet to be determined. 
5. A great number of infection experiments have shown that the conidia 
are probably the only and at any rate the most important agents for the dissemi- 
nation of the Sclerospora-disease. Their restricted longevity is compensated 
by production in large numbers, Earlier workers regarded the resting 
