90 
Proceedings of the Royal Society of Edinburgh. [Sess. 
poised, carried a writing pen tracing the curve on white paper on the 
revolving drum. 
In shoots and leaves, the thread was affixed direct to the organ by 
means of a small linen or worsted collar encircling the tip. 
For roots, the following devices were found workable and satisfactory. 
In the case of stout roots, such as those of the Aroidaceae, a light glass tube 
kept moist was fitted on to the root tip, and this tube was connected by 
thread with the lever. The apparatus is shown in use in fig. 1. 
For more delicate roots a special piece of apparatus was devised (fig. 2). 
This is essentially a (J -tube in which the curved part of the tube is replaced 
Fig. 2. — Sketch of Automatic Apparatus for measuring the growth of Root and 
Shoot simultaneously. 
A, Automatic precision auxanometer with seven days’ drum. B, Tripods and stands supporting 
levers :—/=fulcrum ; r=root lever; s=shoot lever; w=weight. C, Special glass apparatus for 
measuring root growth (turned at right angles to show the parts) : — a, thistle funnel and tube 
fitted with flat cork to which bean is pinned; b , box into which two glass tubes are sealed, 
fitted with two glass windows (through these the two metal pulleys are seen) ; c, cork and tube 
pushed down by root as it grows. Thread attached to cork passes under pulleys and up other 
limb ; d, shoot with collar and thread attached to lever ; e, thread passing to root lever. 
by a metal box containing two light pulleys. The tube is filled with water ; 
in one arm the seedling is fixed with its root depending into the water, 
and its tip in contact with a light float ; from the float a thread passes 
down over the two pulleys up the other arm and thence to the distal end 
of the recording lever. Very accurate counterpoising is necessary. The 
figure shows the apparatus as arranged for recording the growth curves 
of root and shoot on the same drum simultaneously. 
In order to bring out clearly the existence of the four-day periodicity, 
long continuous records are essential ; short records extending over a week 
or so show only one phase of it. The periodicity manifests itself in a 
gradually accelerated growth extending over four days, when a maximum 
