246 
Journal of Agricultural Research voi. xxiii, no . 4 
the plants which induces the nocturnal conidiophore production. Just 
how this layer of moisture operates in this connection is unknown. 
Possibly the layer of moisture is effective by sealing the stomata and 
influencing the gas or moisture content within the substomatal chambers, 
so that this in turn affects the branches of the mycelium located there. 
It seems more probable to the writer, however, that this layer of moisture 
covering the stomatal pores furnishes the emerging conidiophores of the 
Sclerospora the necessary moisture for their development and that this 
development can not take place in the air alone. If this is the case, it 
arouses the interesting conjecture that this relationship may be of phylo¬ 
genetic significance, an indication of steps by which the terrestrial 
Peronosporaceae have been evolved from aquatic saprolegniaceous an¬ 
cestors. 
However, attempts to induce conidiophore production during the day 
by supplying a layer of surface moisture to the infected plants were 
entirely unsuccessful. Plants which had been actively producing conidio¬ 
phores night after night were put in an ice chest and kept at a lower 
temperature for some hours; but although moisture was deposited on the 
inner walls of the container, the leaves, probably because their respiration 
prevented them from reaching the dewpoint, remained free from dew. 
The surface of the infected plant was, therefore, kept covered with a thin 
layer of moisture by repeated spraying. No conidiophores, however, 
were formed, although a darkened ice chest and also a light double-walled 
glass chamber maintained at the same temperature were used in the 
experiments. Moreover, heavily infected leaves of such plants when 
fastened so that they were submerged in jars of pure water produced no 
conidiophores either during the day or at night. These experiments are 
admittedly crude, and it is probable that the processes resulting in conidio¬ 
phore production in the surface layer of moisture are delicate physiologic 
ones which will require careful study under the most exactly controlled 
experimental conditions before they are thoroughly understood. Even¬ 
tually this phase of the problem should be carefully worked ouf; but at 
present, even though the relationship is not entirely understood, it can 
be said that the formation of conidiophores in both species of Philippine 
Sclerosporas—whether on maize, teosinte, sugar cane, sorghum, Sac- 
ckarum spontaneum , or Miscanthus japonicus Anderss.—never takes place 
except when the surface of the host is covered with a persistent layer of 
moisture during the night or very early morning. 
As condidiophore production in these Philippine Sclerosporas has been 
found by the writer to be restricted so rigidly to the night time, it is of 
interest to note whether any such restriction has been observed by inves¬ 
tigators of the other important conidial Sclerosporas of the Orient. 
Apparently Miyake (75) alone appreciated that conidium production 
was nocturnal. Not only Butler (3) in his investigation of Sclerospora 
maydis (Rac.) Butl., in India, but also Raciborski (19 ), Rutgers (20) 
and Palm (16) in their successive studies of 5 . Javanica Palm, of maize 
in Java, failed to grasp this point. To be sure, Rutgers realized that 
there was a relationship between conidium production and moisture, 
since he stated that the fungus in the early morning was like a white 
down on the moist leaves while later in the day when the conidiophores 
and conidia were dried it gave a fine granular effect as of dried salt solu¬ 
tion. Palm (/6), on the other hand, regarded moisture as essential, not 
for the production, but for the germination, of the conidia, and consi- 
