40 BOTANICAL GAZETTE [JULY 
8). Here the retarding action of the inner cells upon the epidermis 
is aided by the compression brought about by the curve. SACHS 
(71, p. 466) has shown that the average length of cells in a curve 
is less than in a straight portion of the root. MacDoucat (49, 
Pp. 352-3) criticises Sacus’ methods and reports the cells on both © 
convex and concave sides longer than those on the same region of a 
normal straight root. His statement that the hairs are “abundant 
on"the regions apical and basal to the region of greatest curvature, 
but are also wholly absent from the region exhibiting the shortest 
radius of curvature,” seems to mean that the roots geotropically 
stimulated elongated at the curve and ceased to produce hair. In’ 
curving roots of corn growing in water, the epidermal cells appear 
to be restricted in their elongation, for curving almost invariably 
causes hair to develop. ScHwarz noted this and called it “nutation”’ 
(75, p- 159). This term did not seem appropriate, and for want 
of a better word “kinking” has been used in this paper. 
Transference from a solution of low osmotic pressure to one of 
high osmotic pressure appears to withdraw so much water from the 
epidermal cells that they do not grow into hairs. When the reverse 
order is followed there is a better chance for the epidermal cells to 
absorb water and to grow before the inner ones, and in this case 
some hairs appeared. The problem of the effect of osmotic solutions 
upon roots is quite different from that relating to filamentous algae 
and fungi. In the last two cases each cell is bathed in the solution 
to be tested, while with roots the action of the neighboring cells 
influences the epidermis, and on account of the thickness of the root 
the inner ones are not affected just as the outer ones. If a solution 
could be made which by its osmotic strength or chemical composition 
would retard the growth of the inner cells and allow the epidermal 
cells to grow, hairs might be expected. In one or two instances 
the epidermal cells of roots of sunflower and corn growing in o.-o.2 N 
solutions seemed to become accustomed to the solution before the 
inner cells, and thus were able to grow out as hairs while the growth 
of the deeper cells was still retarded. 
The retarding effect of diminished food 
of hair on the internodes of the stem of 
note by Kraus (38). 
supply on the production 
potatoes is reported in a short 
In experiments with half seeds, one or two 
pede yeh 2 < 
