MICHIGAN ACADEMY OF SCIENCE. 
33 
was greater (for the first twelve hours) than when A accompanied A, and 
B accompanied B. After about twenty-four hours, this result was not 
nearly so uniform, and after thirty-six hours, it was nearly always reversed. 
The plants which showed the phenomenon most strikingly were corn, and 
squash, and more so with the squash than with the corn. The other plants 
examined were wheat and buckwheat, lupine and corn. 
For the second period, the growth of both radicle and plumule was ex- 
amined, and the period of time was longer than thirty-six hours, and including 
an extent up to about four weeks. The measurements of amount of growth 
during the second period could not be so accurately made on account of 
the extensive root system and the increase in number of leaves and branches. 
But, in a general way, most of the results were so marked and so uniform 
that the actual results were as convincing as those of the first period and 
far more pronounced. In the second period, the results were emphasized 
by growing several — ten or twenty — together in the same vessel, instead of 
a few, as was the case during the first period. 
In a general way distilled water was the medium which proved most satis- 
factory, because it gave results most uniform. Tap water and salt solutions 
were used also, but these seemed to involve problems so complicated as to 
be considered beyond the bounds of the subject at present under particular 
attention. The general results of the experiments in the second period were, 
in a sense, uniform, and were about as follows: 
When plants of the species A were grown with B, they did not develop 
so rapidly, nor produce so much growth in a given time as when grown with 
A. This was very marked with the combination of squash and corn, and 
especially so with the squash; that is to say, of the two plants under con- 
sideration the squash suffered most from the association. 
It ought to be said, perhaps, that it was the root system which offered 
most striking contrast, though the stem system showed similar results. 
When it seemed conclusive by repeating experiments with some plants, 
and by using different plants in combination, that these general results 
were uniform, the real problem of the subject presented itself: — What could 
be the cause of these peculiar phenomena? 
It seemed apparent that the liquid in which the plants had been grown, 
should be the substance which was concerned directly and so this was ex- 
amined from the physiological side, in some detail. As is well known to 
plant physiologists, roots and rootlets shed off to the surrounding medium 
a large number of loose cells from the cap, and from dead root hairs. By 
the aid of a compound microscope, these cells can readily be seen floating 
around in the water drops, and such cells soon decompose by bacteria, which 
also may be seen in large numbers. After a few days, even aquatic fungi 
appear. These fungi live upon the decomposing cells, and upon the ex- 
creted organic matter of plant roots. Moreover, those fungi and bacteria 
excrete in turn a product upon which other bacteria and fungi may act. 
Therefore, the liquid medium of the roots becomes contaminated with at 
least two things directly — (1) plant cells set free by the roots and (2) soluble 
matter. Indirectly, bacteria and fungi which prey upon these substances, 
excrete other products into the liquid. As to the chemical nature of these 
substances, I am at present unable to pronounce further than that they 
are complex, organic substances which rapidly decompose. In fact, because 
of this instability, it is practically impossible to analyze them at this stage, 
for the simple reason that they are not the same one day as another, from 
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