278 BOTANICAL GAZETTE [OCTOBER 
per 1.0 gm. of dextrose. As pointed out later, this nitrogen did 
not appear to be in a form which was available to the fungi. 
In every investigation, all the glassware for the cultures was 
cleaned with the greatest care by being placed for 6-24 hours in a. 
mixture of potassium dichromate and concentrated sulphuric acid. 
rubber for connections 
was new and was first boiled 
in a ro per cent solution of 
sodium hydroxide until per- 
fectly clean. 
Sterilizations were carried 
out in an autoclave raised to 
150 C. at least 20 minutes. 
It was found that tempera- 
tures much above this were 
likely to cause some de- 
composition of the dextrose, 
giving a brown coloration of 
the medium (DvUGGAR 32; 
p- 20). 
Inoculations were made in 
all cases by introducing, with 
a sterilized platinum loop, a 
small quantity of spores from 
a pure culture into about 
rocc. of sterilized distilled 
FIG. 16.—Verticillium chiamydosporium, water in a small test tube. 
Nn. Sp.: @, conidiophores, x80; 6, portion of Then from this one or two 
conidiophore with conidiiferous cells 80; ; 
€, €, chlamydospores, X38; d, ee > drops were transferred to the 
chlamydospores, X380; f, conidia, 380, sterilized culture flasks by 


Poise i § media. Such controls all showed vigorous and char- 
ac beh growth, with the exception of the first investigation as 
explained hereafter, Furthermore, some growth took place in all 
