[Vor. 3 
274 ANNALS OF THE Missourt BOTANICAL GARDEN 
trees, and the nectar of flowers. A second and a third 
series of plates were made from the original colonies, and 
in most cases this was sufficient for obtaining pure cultures. 
Beer-wort gelatin had many advantages over other media, 
such as beer-wort agar, glucose agar, and potato agar, which 
are often used for the isolation of these organisms, On 
agar the growth of bacterial colonies is more rapid than 
that of the yeast colonies during the first period of incuba- 
tion; on gelatin the reverse is true, especially with an in- 
crease of acidity and a higher percentage of gelatin, The 
beer-wort gelatin used in these experiments was made by 
diluting hopped beer-wort with an equal quantity of distilled 
water, and then adding 12-15 per cent gelatin; the final 
reaction of the medium was +5 to +7. 
The 180 different yeast fungi finally acquired were tested 
for growth on blood serum medium at blood temperature. 
It was impracticable to make inoculation experiments on 
animals with all of these cultures. The blood serum test, 
therefore, was made with the purpose of eliminating all 
the cultures that would not grow at 37°C. and presumably 
under some of the conditions that are to be met with when 
an organism is introduced into the blood system of higher 
animals. 
The blood serum medium was made by adding one part of 
nutrient bouillon, obtained from veal, with 1 per cent dex- 
trose, to 3 parts of ox blood serum. The medium was then 
sterilized at 60°C. for one hour on five successive days and 
finally coagulated in an inspissator at 75°C. All the tubes 
were incubated at 37°C. for twenty-four hours in order to 
eliminate any that were not sterile. The yeast cultures 
were then transferred to the blood serum medium and 
kept at 37°C. in a moist chamber for ninety-six hours. The 
growth appearing after this time was examined micro- 
scopically to see if there was any contamination by bac- 
teria. Of the 180 cultures thus tested only twelve strains 
were obtained which grew under these conditions. These 
twelve strains included three red, five white, and four black 
