156 
root tips, tapetum and sporogenous tissue and 
they can be traced as separate individuals through- 
out the .whole process of somatic cell division. 
They also maintain a serial order in which the 
chromosomes appear as individual spheroidal 
masses with a relative place relationship. This ~is 
most clearly in evidence during the prophases. 
In the prophases of the reduction division, on 
the other hand, the chromosomes appear at syn- 
apsis as an extremely thin double thread which in 
the thick spirem stage again appears single. This 
is in marked contrast to the somatic prophases 
where the chromosomes maintain a separate indi- 
viduality which can be traced. In the preparation 
for the reduction division the substance is spun 
out and the chromosomes are so closely connected 
end to end that they can not be identified as indi- 
vidual units. It would appear that in this condi- 
tion the opportunity is given for mutual influence 
and exchange of substance between homologous 
pairs. 
After the reduction division occurs the three 
nuclei which lie at the apex of the wedge-shaped 
spore mother cell divide, making six nuclei which 
then die and become flattened out against the wall. 
The wall of the spore mother cell functions as the 
wall of the microspore. 
In the resting nuclei of the microspores the 
chromosomes appear again as separate individuals. 
Precarious Tests for Chemotropism of Roots: F. 
C. NEWCOMBE, University of Michigan. 
There is probably no part of a plant so sensi- 
tive to so many external stimuli as the tip of the 
root. The root-tip will give tropic responses to 
gravitation, in many plants to light, to moisture, 
heat, chemicals, in many species to pressure, to 
wounds. 
The author has found still another response— 
that to a water-imbibed body in a water-saturated 
atmosphere. A piece of wet filter paper or of 
unglazed porcelain attached to the sloping side of 
the root will call forth a negative curve even in a 
water-saturated atmosphere. This result may be 
due either to a disturbance of hydrostatic condi- 
tions within the cells of the root, or to the accu- 
mulation in the attached body of volatile excre- 
tions of the root. The possible excretions must be 
volatile; for repeated use on successive roots of 
the same bits of paper, without washing, leads to 
no greater response. Either of the two possibili- 
ties assumed above could be interpreted as effect- 
ing traumatropic curves. 
This extreme sensitiveness of the root-tip shows 
SCIENCE 
[N.S. Vou. XXXYV. No. 891 
how precarious are the results of authors who 
think to test the chemotropism of roots by ap- 
plying to the tip bits of paper imbibed with 
chemicals. 
The Nature of the Absorption and Tolerance of 
Plants in Bogs: ALFRED DACHNOWSKI, Ohio 
State University. 
The considerations of the quantitative nature of 
habitat factors, which are rightfully desired as a 
basis for a theory of physiologically arid habitats, 
do not, however, render more clearly the nature of 
the absorption of plants in bogs and the nature of 
their tolerance to toxic substances in peat soils. 
The physico-chemical effects of toxic bodies are in 
part these: they reduce the available water con- 
tent, and they act in varying degree directly upon 
the roots of plants and their functions. Since 
there are (under field and laboratory conditions) 
no differences in the evaporating power of the air, 
in temperature, in greater intensity of light, in the 
gradient of osmotic concentrations and in the pos- 
sible rate of movement of water through the soil; 
and since no morphological limitations in the ab- 
sorption and in the conduction of water (in the 
agricultural plants used) enter into the problem, 
the phenomena of absorption and of resistance to 
desiccation deal, plainly, with considerations of 
the permeability of the absorbing protoplasmic 
membrane, its power of endurance and its ability 
to transform the injurious bodies into insoluble, 
impermeable compounds. A study of the be- 
havior of different species of cultivated plants and 
especially a number of their varieties forces the 
assumption that changes of a cytoplasmic nature 
are particularly important under the conditions of 
growth. 
The Permeability of Protoplasm to Ions and the 
Theory of Antagonism: W. J. V. OSTERHOUT, 
Harvard University. 
Experiments were performed to test the elec- 
trical conductivity of living tissues in various solu- 
tions. The results show conclusively that a great 
variety of ions readily penetrate living cells and 
that antagonism between salts may be explained 
by the fact that they hinder or prevent each other 
from entering the protoplasm. The ions of NaCl 
readily penetrate the protoplasm, but the addition 
of a small quantity of CaCl, greatly hinders this 
penetration. Such salts as KCl, MgCl, CsCl, 
RbCl, LiCl, NH,Cl, NaBr, NaI, NaNO;, Na.SO, 
and Na-acetate act in general like NaCl while 
BaCl, and SrCl, act like CaCl. 
The mechanism of this action is not fully under- 
