1904] CURRENT LITERATURE 389 
current passing through water in which seedlings are growing is not necessarily 
fatal, and that the roots of such seedlings will curve toward the positive pole even 
when the current is of less than lethal strength; second, that ‘negative galvan- 
otropism is not a constant property of any species thus far studied. Since electrons 
instead of ions are the cause of the curve responses the author proposes to sub- 
stitute for Elfving’s “galvanotropism” the term ‘“‘electrotropism.”—RAYMOND, 
H. Ponp. 
NEWcOMBE ‘3 reports experiments on thigmotropism of terrestrial roots 
which show very feeble sensitiveness of the terminal millimeter and of the growing 
region, the few responses being positive and the angle of deviation small. Many 
Ingenious modes of securing continuous pressure and avoiding hydrotropic stimuli 
as far as possible were tried. ‘The most convincing results were gained by sur- 
tounding roots with collapsible collodion tubes, and using a water stream to give 
the pressure. The tubes do not allow appreciable filtration. These experiments 
save strong evidence for the identity of rheotropism and thigmotropism, and 
NewcomBe applies to thigmotropism the results given by his earlier experiments 
on theotropism.'+ The sensitiveness is equal on all sides, and the stimulation 
must extend over a considerable area and be continued for some time to produce 
4 complete reaction. The feeble sensitiveness is probably of no utility to the 
Plant—C, R. B, 
Branpr holds *5 that REINKE errs in thinking the N-content of the sea small *° 
Pecause litle is added to it. His estimates of the yearly addition of organic 
Shige and of inorganic N-compounds by rains would indicate an N- 
P a M sea water that analysis does not corroborate. This discrepancy is 
ny ed by the active dentrification through the action of bacteria, so that the 
aes never surpasses a minute amount. This dentrification has been 
in the i occur and the bacteria have been carefully studied in several eae: 
the chi orth Sea, the East Sea, and even in the Antarctic under the ice. t is 
det s . Teason for the smaller N-content of tropical waters and this difference 
core the lesser amount of plant life there. Branpt believes the N-supply 
and oes without special appeal to such bacterial symbionts as Clostridium 
peerter, though these insofar as they occur may be effective. For 
"hag in the water of Kiel Bay (at 20™) the content in inorganic N is ge 
at of the plankton.—C. R. B 
I . 
1. *NEweomse, F, C., Thigmotropism of terrestrial roots. Beihefte Bot. Cent. 
T8184. 1904, 
4 
Bor. Gaz, 33: 183. 1902. 
15 : vs : * 
Pat Branpr, K., Ueber die Bedeutung der Stickstoffverbindungen fir die Pro 
nim Meere. Beihefte Bot. Cent. 16: 383-402. 1904. 
: " i disponiblen Quellen 
@ Stickstoff. J., Die zur Ernahrung der Meeres-Organismen (Isp ac 
37: ol. Ber. Deutsch. Bot. Gesells. 21: 371-380. 1903- See Bot. 
* 228, 1904. 
