10 J. K. Witson 
The data show that there was a large increase in bacteria per cubic. 
centimeter in twenty-four hours. A further increase is evident with | 
three of the organisms after forty-eight hours. The falling-off in numbers i 
with the other two organisms at the forty-eight-hour period is probably | 
due to their having used all the organic material suitable for growth. 
DISCUSSION OF RESULTS 
The work herein reported shows that in the exudate water from the | 
hydathodes of maize, oats, and timothy, both inorganic and organic | 
materials were found. This was observed in the water from plants | 
varying in age from eight to forty-three days. Color tests were made 
to identify some of the compounds. Since it is recognized that infection | 
by molds or bacteria might change the composition of the water in a short 
time, the exudate water was collected from sterile and non-sterile plants | 
for examination. The total solids were determined by evaporating a 
definite amount of the water and weighing the residue. The weight which | 
was lost when the total solids were ignited was considered organic matter. | 
No effort was made to determine what salts were present in the water | 
other than nitrates and nitrites. This has been determined in a measure | 
by other workers. | 
The organic materials that have been identified suggest that the. 
exudate water may have a similar composition to that of the plant sap. | 
This supposition is especially warranted by the fact that the exudate | 
contains several enzymes which are known to be present within the cell, 
and that the hydrogen ion concentration is almost the same as that of | 
expressed sap of similar plants as reported by Haas. | 
The identification of a substance capable of reducing nitrates to nitrites 
suggests that the nitrates which are taken up by the plant from the | 
substratum are in part reduced to nitrites as they pass up through the plant | 
tissues, and that this reduction may continue for some time after the water | 
has been exuded through the hydathodes. 
The organic material that is present in the water from hydathodes seems | 
to be easily utilized by bacteria. Since under field conditions this water | 
finds its way into the soil, it must serve similarly as a temporary source © 
of food for soil organisms. | 
~ SUMMARY 
The chief points brought out in this paper are the following: 
Total solids in the water exuded through the hydathodes from maize | 
plants growing under non-sterile conditions were as high as 1030 parts per | 
million. The total solids in water from timothy plants which were grow- | 
ing in closed containers in the absence of microorganisms were much less, — 
being in one case only 573 and in another only 220 parts per million. 
In all cases the total solids were more than half organic matter. 
Reactions were obtained which indicated the presence of nitrites, © 
nitrates, materials capable of reducing methylene blue, catalases, and | 
peroxidases, in the exuded water from maize, oats, and timothy. Reduc- |, 
tases were probably present in the water from timothy, but no reaction | 
was Observed to indicate their presence in the water from maize. ) 
