( 344 ) 
leaf veins and from Algae. This suggested to Miss Pekelharing 
that in this way it might also be possible to remove starch from 
the root cap of living roots. It was at once found, however, while 
experimenting with the rootlets of Lepidium sativum , that aluminium 
salts are poisonous. The roots generally react with an abnormal 
growth in thickness and traumatotropic curvatures, by means of 
which they turn away from the aluminium solution. 
Experiments have of late been made with solutions which are 
so called physiologically balanced, i.e. in which the toxicity of one 
metallic ion is annulled or at least compensated for by another 
metal; these experiments led to attempts to counteract the toxicity 
of the aluminium, an object, which was more or less achieved by 
using K-ions. 
If the roots of Lepidium are grown in a solution containing 
1 gram of potash-alum in 4 litres of tap-water, it is found that there 
are a number of roots which become very long and thin and retain 
their starch, while others thicken in a more or less abnormal manner 
and lose their starch. Of the latter there are always some which 
show the above mentioned traumatotropy ^ind which are therefore 
unsuitable for further experimentation. If these are cut away, a 
certain number always remain, which are free from starch and 
straight. If the solution is a little weaker, the traumatotropic rootlets 
indeed disappear, but the starch then persists; in stronger solutions 
the curvature is so general, that the material becomes useless. 
The presence or absence of the starch can be ascertained by means 
of chloral-iodine; in the transparent rootlets of Lepidium it is then 
possible to see at once by small magnification, whether or not starch 
is present; increased certainty is obtained by making longitudinal 
sections. In order to be absolutely sure, however, a series of micro¬ 
tome sections were made in certain cases, and each section was 
examined separately for starch; it was thus found that the chloral- 
iodine test is sufficiently reliable. 
The experiment was now carried out in such a way, that the 
seeds were soaked in water for a day and then placed on gauze 
which was stretched over a lamp chimney. The chimney-glass was 
placed in the solution of potash alum in such a way, that the level 
of the liquid was */, cm. below the gauze. After a few days the 
rootlets which had grown through the gauze, had attained a suitable 
length. Those with traumatotropic curvatures were then removed, 
and the lamp-glass was placed horizontally in order to expose the 
roots to the stimulus of gravity. All experiments were carried out 
in the dark, in order to exclude the action of light. 
