398 
R. P. HIBBARD 
bility of deleterious root excretions from lupine seedlings. We must 
admit in the beginning that we have not isolated any toxic substance 
from the water in which these seedlings have been growing. The 
quantity of poison is obviously so small that it will necessitate the 
evaporation of lo or 12 liters of solution to get enough residue for a 
chemical test. The difficulty of this problem is still further increased 
since organic chemists can give us no universal method of treatment 
applicable to all unknown solutions. Previous literature gives us 
assurance that the excretions are probably organic in nature. The 
probability is that the substances excreted are compounds of multiple 
function, and if they do contain an acid radicle, this radicle must be 
internally compensated with some basic group, since the solution 
gives no reaction to the ordinary indicators. If an aldehyde is sought 
for we meet with a difficulty in that we have no differential test to 
indicate what aldehyde it may be. 
On the other hand, we have one or two indirect methods to attack 
this subject of toxic excretion. After a certain length of time in 
distilled water lupine roots display certain characteristic features not 
noticeable in tap water cultures. Roots in tap water are long, slender, 
grayish white, usually straight and firm. A large conspicuous root 
cap covers the tip. The water does not become turbid. In distilled 
water the roots present quite a different appearance. They are 
covered with a felt-like coating which at first gives the appearance of a 
mass of root hairs or a weft of fungus mycelium. It is believed that 
this is nothing more than root cap tissue hanging on the root as the 
tip pushes forward. On closer examination under the microscope this 
material does not present the characteristic structure of root hairs or 
fungus hyphae and resembles in every particular the cells of the 
outer layer of the root cap. No reason is hazarded for its abundance 
in distilled water. It has not been noticed in tap water, and appears 
less abundant in distilled water that has been changed two or three 
times daily. This weft of tissue falls off and gives the water a turbid 
appearance. In distilled water the roots are shorter, thicker and 
usually more or less bent near the tip, showing the tendency for 
fishhook formation. The lateral roots appear earlier and are more 
abundant in distilled water cultures than in tap water cultures. 
They show all the appearances of roots suffering from slight doses of 
poisons. In all probability the roots excrete a toxin which retards 
growth. If this toxin is removed by frequent changes of the water 
