RELATION BETWEEN VEGETATIVE VIGOR AND REPRODUCTION 57 1 
An apparent exception to the statement that levulose is as good a 
food for vegetative growth as maltose is found in the results shown in 
Table XVI. At the completion of this series (IX) it seemed difficult 
to account for the small amount of dry weight out of the peptone- 
levulose solution compared with that out of peptone-dextrose and 
peptone-maltose. On comparison of the conditions under which the 
various series of experiments had been made, it developed that the 
levulose used in the earlier experiments had been from a certain lot 
from Kahlbaum. The supply being exhausted and no more from the 
same source being available, the solutions for series IX were made up 
with levulose from Schuckardt. It seemed probable therefore that 
the smaller weight could be accounted for by the difference in the 
quality of the levulose. To test this the small amount remaining in 
the original Kahlbaum bottle was carefully collected and two lots of 
two times 100 cc. each of a solution containing o.i percent peptone 
and 1/50 molecular levulose were made up, one set with the Kahlbaum 
and one with Schuckardt levulose. After being inoculated with 
S. monoica the solutions were allowed to stand 20 days and the mycelia 
were then dried and weighed. The average weight of one lot out of 
the Kahlbaum levulose was .0212 milligrams, and out of the Schuckardt 
lot .0082 milligrams; practically the same degree of difference as that 
existing between the weights of mycelia out of peptone-levulose solu- 
tions recorded in Tables XV and XVI. It was not possible to under- 
take an analysis of the sugars from these two sources but the organism 
clearly recognized a difference between them. This experience per- 
haps suggests one of the reasons for the sometimes contradictory 
results secured by different workers. The reactions of living things to 
their surroundings are extremely delicate. Not only must the inherent 
characters of different species be considered, but in each species there 
are most probably a number of strains each of which makes its own 
peculiar response to a given set of conditions. Add to this the effects 
produced on a certain organism by supposedly chemically pure sub- 
stances from different manufacturers and the conditions are present 
for varying results from which conclusions may be drawn leading to 
endless controversy. Possibly the result which Klebs reported, that 
S. mixta made a better growth in sucrose, dextrose and maltose than 
in levulose may have been due to the use of a poorer levulose than 
that which the writer used in the earlier series. 
