62 ACROTHECIUM PENNISETI 
turn brown or greyish brown in colour. These chlamydospores either remain 
united in a chain or separate, and often germinate to give rise to new hyphe 
(Plate III, figs. 1—3). 
(c) Growth of fungus on different culture media. A comparative study of the 
growth of the fungus has been made on 20 different culture media. Two 
tubes of each medium were inoculated on the same day and all these tubes were 
kept at the room temperature which was between 20 and 23°C. Media of 
known reaction were employed and the reaction of each is indicated with the 
cultural description. All the media used were acid in reaction, ranging from 
+2 to + 9 Fuller’s scale. The composition of the media is given at the end 
in the Appendix (p. 72). 
The fimgus can grow well on most media tried, but does best on potato 
juice agar, wheat broth agar, nutrient glucose agar and French-bean agar. 
In all of these growth was profuse and the mycelium spread even on to the 
walls of the tubes. Conidia were formed in large number except on French- 
bean agar, on which only a few spores were observed. Of the above four 
media, potato juice agar and wheat broth agar were the best, both as regards 
the growth and production of spores. Besides these a fair growth was also 
found on the other meal agars described below. The growth was poor on 
glycerine agar, cellulose agar and on corn leaf juice agar. Details of the growth 
on all the media are given below. 
1. Potato juice agar (+6 Fuller’s scale). The growth is best on this 
medium. Woolly aerial mycelium fills three-quarters of the tube 
in a few days and spreads on the walls. The colour in the 
beginning is light grey, but later on it changes to dark grey. 
There is a slight tinge of pink present on the sides where the 
medium and the tube meet. In six days the growth is very 
profuse and the tube is quite full; the mycelium becomes darker 
and the medium gradually turns yellowish in colour. The 
creeping hyphe are subhyaline and in older cultures they become 
olive brown. They are up to 7’5m in diameter. Thick-walled 
dark brown chlamydospores are also formed. Spore formation is 
very free and sometimes, in the older cultures, the conidia 
develop below the tip of the conidiophores. They measure 
15—20u * 10—12°5y. 
2. Thaxters hard potato agar (+6 Fuller's scale). Growth poor at first 
but later on fairly good. The medium becomes slightly yellowish 
near the margin in the beginning and then tuins darker gradually. 
Aerial growth is moderate, dark olive grey in colour. The 
appearance of the growth is somewhat like that on nutrient 
