2 JO 
Journal of Agricultural Research , voi. xxiii, no. 4 
to some extent by the moisture on the dew-covered plants, none the 
less a considerable number were collected on maize during conidium 
production. These included such diverse forms as several types of 
leaf-eating larvae, many kinds of ants, and a variety of grasshoppers, 
leafhoppers, Phryganids, Hemiptera, and Coleoptera. On examination 
it was found that the appendages and bodies of these insects often had 
adhering to them large numbers of conidia which germinated readily 
when placed in dew or on agar. Moreover, in the leaf-eating larvae 
such as Plosia sp., the intestine and even the excrement showed conidia, 
some of which proved capable of germination when tested. Since the 
carrying of conidia by insects is apparently of very little importance in 
comparison to other methods of distribution, no attempt was made to 
secure further experimental data on frequency of inoculation or distance 
of spread. It seems clear, however, that occasional infection may occur 
in this way. 
Moist soil with conidia adhering probably serves infrequently as a 
contributory means toward securing distribution of the downy mildew 
by other agencies. The damp earth under the low-hanging leaves of 
small, heavily infected plants occasionally, after still nights, was seen 
to be whitened with innumerable conidia. Examination showed that 
these retained their vitality and germinability on the soil until dried 
by the early sun, while such conidia as were lodged in protecting crannies 
lived even longer. Moreover, the infection of germinating maize seeds 
that had not yet emerged from sterile sand was easily accomplished 
by using bits of this conidium-laden soil as inoculum. The seeds were 
uncovered, bits of infective soil were placed on their plumules, the 
sterile sand was replaced, and the pots were protected from further 
infection. The resulting seedlings were heavily diseased. Undoubtedly 
seedlings when emerging or just at the surface of the soil are occasionally 
infected in a somewhat similar fashion in the field. It is probable, also, 
that such conidium-laden soil is at times splashed about and causes the 
infection of adjacent maize plants quite as the sporangia of Pythiacystis 
were found by Smith (23) to reach and inoculate low-hanging lemons 
in bits of spattered earth. Furthermore, it is possible that infective 
soil could be carried to susceptible young plants by animals, or implements 
or men. In practice, however, such obstacles as, first, the necessity 
that the infective soil should be transported before or shortly after 
dawn, and, second, the necessity that it should reach the susceptible 
protected parts of the host, would probably prevent this method of dis¬ 
tribution and infection from operating in any save rare instances. 
DISSEMINATION OF THE PHILIPPINE SCLEROSPORAS 
The foregoing discussion of conidium production and dispersal logically 
leads us to consider the broader subject of the dissemination of the 
Philippine Sclerosporas. The dissemination of such fungi may be con¬ 
veniently divided, as Butler (4) has shown, into two general types; 
first, discontinuous over comparatively limited areas by means of a 
succession of short jumps; second, continuous over large extents of land 
or water without interruption. Spread of these diseases in the Philip¬ 
pines comprises both types. It is chiefly local and discontinuous, involving 
short successive steps from field to field and region to region. To a 
limited extent it is also continuous, involving longer unbroken jumps 
from island to island over intervening seas. Spread of these diseases to 
