jan. 27,1923 Production of Conidia in Philippine Sclerosporas 251 
has matured and is being discharged at 2 a. m. It should be emphasized, 
however, that this process is a continuing one; for during this time other 
conidiophores have been developing from the initials, so that from thence¬ 
forward a constant succession of conidia is developed and discharged. 
Although the maximum discharge of conidia usually takes place from 
2 to 3 a. m. and lessens somewhat after that time, it does not entirely 
cease until the necessary moisture is dried by the early sun. This schedule 
applies consistently under the condition of uninterrupted dew which 
usually obtains during clear nights in the Philippines whether in dry, 
wet, or transitional seasons. 
During rains, however, this schedule may be altered. When gentle 
rain begins in the afternoon and continues so that the plants have already 
been wet two or three hours by the time dew deposition begins, the 
formation of conidia takes place much earlier, beginning even as soon as 
9 o'clock, reaching its maximum around midnight, and continuing under 
favorable conditions till dawn. 
Observations made on May 24, 1919, furnish a good example of such a 
schedule. After a hot, humid day with a maximum temperature of 93 °F., 
rain began at 4 p. m. and fell steadily for more than an hour. The sky 
remained clouded and the air, which was full of moisture, cooled rapidly, 
reaching 75 0 shortly after sunset and causing an early and heavy deposi¬ 
tion of dew. At 8 p. m., when their surface had been moist uninterrupt¬ 
edly for 4 hours, infected maize plants were inspected. Microscopic 
examination showed that conidiophore production was indeed beginning, 
the conidiophores being in the earliest stages of development as club- 
shaped initials. At 9, development of the conidiophores had progressed 
further and the whitish down was visible under a lens. At 10, heavy 
conidiophore production was apparent, and quantities of conidia were 
matured. This production reached its maximum from about 11 until 
midnight but still continued, although less abundantly, at 5 the next 
morning, when the sun was just appearing. On plants protected from 
the early sun conidia were formed for about an hour more before drying. 
Production of mature conidia in this case continued for more than 8 
hours instead of the 4 or 5 of the usual schedule. 
When, after a night of abundant dew, the sky clouds over and a 
gentle rain begins at dawn, so that the necessary moist condition of the 
leaves is maintained into the morning by a constant drizzle, the process 
of conidium production may continue for a few hours longer. Similarly 
when maize is located in deep valleys or protected from the first rays of 
the sun by the shade of trees or hills, the dew on the infected leaves and 
the consequent production of conidia persists after the process has 
ceased on the already dried leaves of less sheltered plants. 
During the dry season, also, the usual schedule may be altered. 
Occasionally conditions of temperature and moisture are such that dew 
deposition is very light and fleeting, and conidiophore production, 
beginning tardily, is scanty, restricted to moister parts of the plant 
surface and soon ceases. For example, on April 23, 19x9, one of several 
successive dry, partly cloudy days, although the temperature, which 
had been 92 0 F. about noon, dropped gradually to 75 0 during the night, 
dew deposition was very late and scanty, as the sky was clouded and a 
warm, dry breeze blew fitfully. Frequent examination of infected 
maize plants showed that a very light dew began to gather at xo p. m. 
At 3 a. m., in a thin film of dew on the leaves, a scanty production of 
