146 BOTANICAL GAZETTE | AUGUST 
inconceivable that they should produce an effect great enough to be propa- 
gated through many cells and produce a reaction. It seems much more 
probable to us that the sensitiveness is due rather to a chemical than to a 
physical change of condition within the cells. This seems the more probable 
on account of the fact that when the grains leave their normal position, the 
protoplasm here becomes changed. Possibly this may be due to the removal, 
not of the grain, but of the leucoplast in connection with it. The chemical 
effect of the leucoplast upon sugars passing through it is very great (since it 
produces in them condensation to form starch), and it may well be that it also 
has an effect upon the surrounding protoplasm. There may be other, as yet 
invisible, substances within the cell, which cannot diffuse readily, whose 
specific gravity differs from that of the protoplasm, and these might affect the 
protoplasm unsymmetrically, thus setting up a stimulus which could be prop- 
agated to the curving region. 
The second paper? treats of the conduction of the stimulus from the 
sensitive regions to the region of the curvature. Traumatropic responses in 
roots were chosen as field for experimentation. If the tip of an Allium root 
is wounded by a cut or needle thrust, the protoplasm of the meristematic 
cells bordering upon the wound heaps up and becomes more dense on the 
side toward the wound. The nucleus also migrates toward the wound, often 
coming to lie against the wall on that side of the cell. After a very short 
time these cells regain their normal condition. But in the meantimea second 
and third layer of cells, at the side of and behind the wound, have responded 
in the same manner. Thus in roots killed 15 minutes after wounding, the 
response has been propagated through 1.25 ™™ of tissue, but those cells within 
1™™ of the wound have already regained their original condition. This 
propagation takes place most rapidly in a longitudinal direction, but only 
towards the base of the root. It also occurs in both directions laterally. 
A careful investigation was made to determine whether this difference in 
the rate of propagation of the response might correspond to any difference in 
structure. In the cells taking part in the traumatropic reaction, longitudinal 
strands of protoplasm can, by proper staining, be made visible with compara- 
tively low magnification. Sometimes there is a single strand, sometimes Sev- 
eral; sometimes they lie near the middle of the cell, and sometimes, 
especially in vacuolated cells, along the lateral walls. The 
always in contact with the nucleus, often dividing and enclosing this body 
between several branches which reunite beyond it. A differential stain for 
the branches has not been discovered, but they take the ordinary stains pusich 
more deeply than the surrounding protoplasm. The best results were obtaine 
by staining strongly with fuchsin S. 
2 NEMEC, B.: Die Reizleitung und die reizleitenden Strukturen bei den Pflanzen. 
8vo. pp. iv-+ 154. pls. 3. figs. zo. Jena: Gustav Fischer. 1901. Cf. note Bor: Gaz. 
3x: 133. 1901. 
