Jan. 27,1923 
Production of Conidia in Philippine Sclerosporas 273 
this stage alone was found on mid grasses in remotely isolated uplands 
far from maize, and on islands two or three miles from shore. 
The three oogonial Sclerosporas, although morphologically similar, 
occur on three different hosts and are occasionally found in widely 
separated localities. The conidial Sclerosporas are morphologically 
separable as two distinct species (25). It is impossible, at present, to 
understand what relationship, if any, exists between these conidial and 
oogonial stages. From the evidence at hand it is not apparent whether 
the conidial Sclerospora philippinensis, found on maize, sorghum, and 
teosinte, and inoculated to Saccharum spontaneum and Miscanthus 
japonicus , has as another phase in its life cycle the oogonial stages found 
on one or more of the three hosts mentioned above, and whether the 
conidial Sclerospora spontanea found on maize, Saccharum spontaneum , 
and sugar-cane, and inoculated to Miscanthus japonicus is related to 
these oogonial forms, or whether all are independent and unrelated. 
The solution of this relationship necessitates germinating the oospores 
and securing conidial infection from inoculation with them. So far the 
writer's preliminary investigations of these points have resulted unsuccess¬ 
fully, as have all the attempts reported in the literature by investigators 
of the genus from its founding by Schroeter (22) in 1879 to the present 
day. To be sure, in 1884, Prilleux (18) reported that M. Frechou, para- 
macien of Nerac, had seen the oospores of Sclerospora graminicola germi¬ 
nate by the protrusion of a hypha; but this investigation was not followed 
far enough to cast any light on the relationship of the two stages. Until 
this relationship is worked out, the part played by oospores in distributing 
and maintaining the downy mildews in the Philippines can not be under¬ 
stood. 
When considering the Philippine Sclerosporas as a source of danger 
to the United States it is chiefly with the oogonial stage that we are 
concerned. Introduction probably would be accomplished by oospores, 
for as has been seen the fungi could not survive distant transportation 
except in this stage or as mycelium in sugar-cane or grass cuttings. If 
established in our country the Sclerosporas would survive the winter 
principally by means of the oospores which with their adherent oogonia 
are characteristically thick-walled and resistant. It is in this way that 
the closely related Sclerospora graminicola which thrives in the Tropics 
is able to live through the year in northern Iowa, Wisconsin, and Michigan. 
For these reasons the detailed study of the oogonial phases both of the 
Philippine Sclerosporas and of other species is one of the most pressing 
needs of future investigation. 5 
DISSEMINATION BY MEANS OE CONIDIA 
It is the conidia which play the most important part in disseminating 
the downy mildews of maize throughout the Philippine Islands. From 
a knowledge of the details of conidium production and dispersal which 
6 It is of interest to note that since the foregoing was written Sclerbspora macrospora has been found on 
wheat in the United States. Wheat plants attacked by this fungus were collected at Jordan, Ky., in April, 
1921, by Mr. R. W. Leukel and identified by Dr. A. G. Johnson, who later found the same parasite on spec¬ 
imens of wheat collected in California in 1919. Subsequent investigation by the writer has shown that the 
Sclerospora is well established m the wheat fields of western Tennessee and Kentucky. This species has 
never been fomid in the Americas before, but in Italy, southern Erance ,*and other parts of Europe it has 
been known since 1895 as a disease sporadically destructive to wheat, maize, oats, rice, and various wild 
grasses. Its occurrence in Tennessee, far from wheat, on Bromus commutatus Schard., a grass introduced 
from Europe within comparatively recent years, possibly indicates that this host brought in the disease 
with it. In any case, this instance emphasizes the danger of the oogonial stage, the only one known in 
this species as a means of disseminating Sclerosporas. 
