220 
Journal of Agricultural Research 
VoL XXVI, No. S 
was air-dry, the blocks were placed in boiling distilled water for about 
five minutes and then in cold distilled water, in order to increase the 
moisture content. The blocks in bundles of five were then sterilized 
for an hour under 5 pounds pressure in an autoclave. Besides the test 
blocks, irregular-shaped culture blocks of mixed hardwoods were pre¬ 
pared to serve as a foundation in the flasks. These were kept in distilled 
water at about the boiling point for several hours. Cold water was added 
to saturate the blocks, and they were sterilized under 10 pounds pressure 
for an hour. 
FLASK CULTURES AND THEIR INOCULATION 
Twenty-two flask cultures (duplicate series for the eleven molds used) 
were then prepared as follows: A layer of cotton linters was placed on 
the bottom of a liter flask. One hundred and fifty cc. of distilled water 
were poured in and the cotton made to lie flat on the bottom of the flask. 
A number of culture blocks sufficient to cover the bottom were then 
added and on top of these were placed five test blocks of each species. 
The mouths of the flasks were closed with cotton plugs, capped with a 
layer of cotton and a layer of cloth and firmly fastened down. 
The flasks were then sterilized, first for 30 minutes under 12 pounds 
pressure, then after 24 and after 48 hours, for 1 hour without pressure. 
In the meantime, water blanks were prepared and sterilized (20 cc. dis¬ 
tilled water in a plugged test tube). Inoculations were made by the 
spore suspension method. A sterilized wire loop was dipped into the 
water blank and then inserted under sterile conditions in a stock culture 
of the mold to be used. The adhering spores were then deposited in the 
water in the test tube, which was shaken well and poured into the pre¬ 
pared flask. 
SPECIES OF MOLDS 
Penicillium luteum Zukal., P. rugulosum Thom, P. divaricatum Thom,. 
Aspergillus fiavus var., A . niger van Tiegh., Monilia sitophila (Mont.) 
Sacc., Cephalothecium roseum Cda., Graphium sp., Ceratostomella sp.,. 
Mucor sp., and an unidentified form which is very commonly found on 
Sitka spruce and red oak, were used. 
The cultures showed growth three or four days after they had been 
inoculated. The early growth was abundant on the surface and fluffy 
(PI. 1, A, B, C, G, H). The cultures were placed in a partially darkened 
cabinet, where they were frequently inspected, and here they were allowed 
to develop at room temperature for a period of almost two years. By 
May, 1921, signs of drying were apparent in the cultures, the general 
appearance of which at that time is indicated by Figures D, E, F, and 
I in Plate 1. 
Inspection on this date showed one series of 11 cultures, one of each 
mold used, to be still somewhat moist and apparently alive. These 
were set aside in order that they might continue to grow and reach the 
greatest development possible. 
Some of the duplicate cultures of these molds had become contaminated 
during the two years' growth, but five were pure—namely, Aspergillus 
niger , Ceratostomella sp., Monilia sitophila , Penicillium divaricatum , and 
the unidentified form (No. 71218-1). These were opened and transfers 
were made. The test blocks were then preserved for sectioning in a 
solution of formalin and alcohol (6 cc. 40 per cent commercial formalin 
to 100 cc. 50 per cent alcohol). The transfers were made under sterile 
