44 C. Hunter and E. M. Rich 
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faltung verschiedener Pflanzenorganen. Bot. Zeit. 1863. Gesammelte 
Abhandlungen , 1 , pp. 179-228. Leipzig, 1892. 
(23) Shive, J. W. A Study of Physiological Balance in Nutrient Media. 
Physiological Researches, 1 , pp. 327-397. 1915. 
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feuilles. Rev. gen. de Bot. 2, p. 369. 1889. 
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die damit zusammenhangende Vermehrung der Aschenbestandtheile 
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pp. 46-53. 1891. 
LABORATORY NOTE 
An Apparatus for the Measurement of Stem 
Elongation 
By C. HUNTER and E. M. RICH 
T n the course of an investigation recently carried out in this depart¬ 
ment it became necessary to compare the rates of elongation of 
the stem of Impatiens Balsamina during relatively short intervals of 
time. The horizontal microscope proved to be unsuitable for this 
purpose and the various forms of auxanometer were found to be 
insufficiently sensitive. Eventually a satisfactory apparatus was 
devised which, it is thought, may be of use in laboratory practice. 
The lower end of a piece of glass tubing (C) 5-7 mm. in length, 
drawn out as fine as possible, and sealed off in a flame, rests in the 
axil of a small leaf in close proximity to the growing point. C is 
maintained in a vertical position by means of a glass tube (T) of 
slightly larger diameter which is attached to the edge of a microscope 
slide by means of Canada Balsam. The upper end of C bears a square 
horizontal platform of mica ( M ) whose side is 0-5 cm. On the upper 
surface of M a small flat piece of platinum foil (E) is fixed with 
shellac. A fine insulated copper wire is in contact with the platinum 
foil and is connected at its other end to a resistance ( R ). This is con¬ 
nected through a galvanometer ( G ) with a battery of dry cells (B), 
and to a spherometer (S) rigidly clamped above the plant and adjusted 
so that its central point is immediately above the platinum electrode 
E. The attachment CME can slide freely in T, and, consequently, as 
