Jan. 27,1923 
Production of Conidia in Philippine Sclerosporas 259 
leaves of the maturing host wither, it finally ceases to support conidium 
production after months of activity. The extent of the discolored coni- 
dium-bearing areas on plants of various ages has been determined for 
the different maize types most common in the Philippines. The least 
area is found in the case of such small, rapidly maturing varieties as 
Manobo and Davao Waxy Maize and the dwarf native flints. The maxi¬ 
mum area occurs in such large, slowly maturing types as introduced 
American dent varieties or those strains, such as “Moro” White, devel¬ 
oped from dent-flint crosses. Between these two extremes lie the interme¬ 
diate areas which are typical of the medium-sized, moderately rapidly 
maturing yellow and white flint types that are so commonly grown 
throughout the islands. 
In order to gain an idea of the extent of the conidium-producing areas 
of diseased plants under the usual field conditions, measurements were 
made of characteristically infected specimens both of the common 
native-grown maize and of the introduced types under cultivation at the 
college. Some of these measurements are .shown in Table II. In 
obtaining these data the following method was used: Leaves bearing 
conidiophore-producing areas were carefully removed from infected 
plants and pinned down to large sheets of paper upon which the outline 
of the whitened areas was carefully traced through the tissue of the leaf 
with a sharp stylus. The space inclosed within these tracings was then 
computed by means of a polar planimeter. Only portions which were 
found by actual observations to be producing conidiophores were 
included. In the specimens tabulated, therefore, the measurements 
give a fair idea of the amount of surface on which conidiophores were 
borne. The extent and general configuration of this surface on the 
successive leaves of two of the plants included in Table II are shown in 
Figure 1. 
To the second factor, the number of stomata in the conidium-bearing 
surface, the quantity of conidia produced is also directly proportional. 
In no case were conidiophores developed except from the stomata, and 
in the manner already described. The stomatal frequencies recorded by 
Eckerson (<?), Duggar (7), Kiesselbach (jj), and others show a wide 
range of variation not only between different individuals or varieties 
under similar or diverse environmental conditions but also between 
different parts of the same plant. In the present instance, therefore, 
no extensive counts were made, but enough material was examined to 
determine that in the principal types of infected maize studied in the 
Philippines the stomatal frequencies fall easily within this range. In 
such varieties as Manobo Waxy, the number agreed closely with Kiessel- 
bach’s counts for Chinese Waxy; while in the large flint-dent crosses, 
such as Moro White, the number closely approximated his counts for 
various dent types. In general, it was found that his averages of 77 and 
93 per square mm. of upper and lower surface were sufficiently con¬ 
servative to serve as fair mean values for calculation in the Philippine 
maize varieties studied. 
