40 BOTANICAL GAZETTE [JANUARY 
of cortex often curve far out from the axis, then rapidly come 
back up to it. The movement takes place within a few seconds 
and can be followed by the unaided eye. Whether the cortex 
spreads or not, almost without exception, so far as the observa- 
tions went, the two strips of cortex at first became considerably 
shorter than the axis. The latter shortens much more slowly 
than the former, but after five minutes it has become shorter 
than the cortex and so remains. 
I can think of two reasons why the cortex plasmolyzes more 
rapidly than the axial cylinder. The many intercellular spaces 
in the cortex allow the plasmolyzing agent to reach the cells 
more rapidly in this tissue. At the same time the abundant 
protoplasm in the cells of the axial cylinder may offer a greater 
resistance to the exosmosis of water than the thin layer of pro- 
toplasm in the cortical cells. 
TABLE XIII. 
MEASUREMENTS OF CURVING ROOTS. 
First half cm. of concave side, 
Dat 
hor Roots used Became longer Did not lengthen Shortened 
March 20 5 2 _ ; 
24 3 2 I 
25 5 2 2 I 
April 16 6 5 : 
Mi 6 5 I 
25 as Il 3 
44% . 44% 12% 
This table shows that there is not merely a relative shorten- 
ing of the concave side, but in almost half of the roots tested 
there was no growth in length at all on the concave side in the 
first 0.5 from tip, and in 12 per cent. there was an actual short- 
ening in that part. 
The roots were marked off with India ink, some in I™™ 
Spaces, some in 0.5°", and then branded. After the. curve had 
made some progress they were measured again. The time 
varied from two to seven hours after branding, according to the 
