i6 
Colorado Experiment Station 
killing the leaves, for if the leaves alone are killed the tree may put 
out others and go on living, if we don’t take off the leaves too often, 
but if we kill or injure the root hairs so that the tree cannot get either 
food or water enough its leaves burn, perhaps wilt if the action on 
the root hairs is sudden enough and it dies. I have seen the leaves 
burn on very many trees, thousands in this case is no figure of speech, 
and I have also seen the still green, full-sized leaves just wilt and hang 
limp. These trees all died. There are difficulties in making the dif¬ 
ferent things that we have learned about these matters agree or con¬ 
sistently apply, but it may be that a nitrate solution of a certain 
strength may kill the root hair by poisoning just as the sodic arsenite 
killed the leaves and the living part of the limbs, trunk and root, 
whereas it did not act on the root hairs in such a way as to prevent 
its being taken up. If a nitrate solutiop will act in such a manner as 
to stop the taking up of water, whether it acts by poisoning or purely 
in a physical manner, the result is the same. 
ONE SALT MAY MODIFY ACTION OF ANOTHER 
The different salts act differently, some may under no conditions 
act as a direct, poison but simply in a physical manner by their osmotic 
pressure. Further, the presence of one may modify the action of 
another. Magnesic sulfate, for instance, in pure solutions, has been 
found to be very poisonous, pretty nearly the most poisonous salt, but 
this don’t seem to hold in the field. Experiment shows that seedling 
roots can just live in a solution containing 7 parts of magnesic sulfate 
in ioo,cxv:> parts of water, but I found the roots of four-year-old alfalfa 
plants V hich were more than 12 feet long and extended i foot below 
the level of the ground-water, which was bitter to the taste and carried 
852.5 parts of mineral matter in each 100,000 parts of the water. One- 
tenth, or 85 parts of this mineral matter was magnesic sulfate. We 
have in this ground-water twelve times as much of this salt in 100,000 
parts as the experiments given showed to be the limit that plants could 
tolerate and yet these roots were living and the plants were thrifty. 
This field yielded between 4 and 5 tons of hay per acre the year that 
this sample of water was taken, and continued to do so for years after¬ 
ward. This difference between the results of laboratory experiments 
and the facts of the field is well known and the explanation offered 
is that pure solutions of these salts act differently from solutions of 
mixtures. In the case of the ground-water just mentioned carrying 
twelve times more magnesic sulfate than would be necessary in a 
solution of this salt alone to limit growth, there were also other salts 
making up nine-tenths of the whole and the presence of these other 
salts, sodic sulfate, calcic sulfate, calcic carbonate, magnesic chlorid 
and carbonate, kept the strong solution of magnesic sulfate from doing 
