122 
IOWA ACADEMY OF SCIENCE 
All the plants were inoculated with the clover bacteria on August 6th. On 
August 10th all the pots had a stand of from fifteen to twenty plants, and they 
were thinned down to ten plants per pot. The plants in all the pots were 
healthy and on a par. 
By August 23d, pot 513 began to look unthrifty. The leaves lacked chloro- 
phyl and the plants soon began to drop behind the others, and in another month 
they were all dead. There was considerable growth of algse over the surface 
of the sand, tinder the microscope this was seen to be an unicellular plant 
gathered together in clusters. The species was not determined. This pot was 
very evidently diseased, and it is taken out of the reckoning. 
By August 23d the manured pots began to drop behind the pots treated with 
the nutrient solution, and they were given the second application of 117.5 c. c. 
of manure leachings to each pot. 5 c, c. of the nutrient solution, diluted to 
117.5 c. c. were also given at this time to the pots that had received this treat- 
ment at the beginning. Three days later it was seen that several of the plants 
in the pots treated with manure leachings were suffering from the application 
last given. They were watered to dilute the toxin as much as possible. By 
September 18th all the plants on pot 511 were dead. Over half the plants on 
the other manured pots also died before the end of the experiment. 
It is seen by studying the data given above that the clover in all the pots 
started off together and grew well, showing that the sand was a good medium 
in which to grow the clover. This also disposes of the question of any ill 
effects arising from the toxins thrown off by the germinating clover. Any 
such toxin was in such minute quantities that it did not affect the growth of 
the clover. The check pots show this. The clover on these pots made a normal 
growth for the first four weeks, after which it grew but little, but most of it 
lived until the end of the experiment, which ran eleven weeks. 
The manured clover at the end of six weeks showed only a slight gain over 
the checks. This gain showed that the manure did furnish some plant food to 
the clover, but it was very little. The manure was evidently poisoning the 
clover, for one-fourth of the plants were dead at this time, and three-fourths 
of them were dead at the end of the experiment. Considering the condition 
of the clover at the close of the experiment, it is seen that only a few of the 
manured plants received any benefit from the manure, and they only to a slight 
extent. 
In striking contrast to the behavior of the manured plants, were the plants 
fed by the nutrient solution. These grew without any check, in a normal 
manner, showing perfect nourishment, leaving out of consideration the dis- 
eased pot. At the end of six weeks they were four times as big as the manured 
plants, and at the end of the experiment the weight of the tops per plant was 
over ten times that of the manured plants, and the weight of the roots eight 
times as much. 
In brief, the nutrient solution was a good plant food under these conditions, 
and the manure by itself was not. It might be thought as an explanation of 
its lack of feeding power for the clover, that the proper bacteriological changes 
did not take place in the manure extract because the sand differed so from the 
soil. There are two answers to this: In the first place the sand was not kept 
sterile, but was at all times open to inoculation from the air and the dust of 
the room. The sand was also inoculated with a soil extract as noted, and it 
had every chance to become filled with soil bacteria. In the second place, the 
