; a. 
e. 
od 
tips of tendrils by means of loops of soft cotton cord to de 
termine their lifting strength. With weights less thanst 
grams many close spirals were formed lifting the weights 
several centimeters. With the increase of weight, moreoptt 
spirals resulted. Still higher only weak curves were male 
while tendrils weighted with twenty grams were held entirely 
straight, and this may be safely taken as the limit of the lift 
ing power (fig.3). These effects, however, are modified by ef 
fect of the traction of the weights on the tendril.’ 
The results obtained by the dynamometers are doubtless @ 
128 The Botanical Gazette. 
ity balance. The tendril is fastened to the lower end of 
spring and the amount of tension determined by an arbitrary 
scale. The second form was the lever dynamometer Wi 
is in general use and needs no description here.* < 
The most satisfactory results, however, were obtained fre 
the use of Véchting’s dynamometer.® This machine 6” 
signed for use with a clinostat, but can be used in pa 
an 
ble. (See plate X.) It consists essentially of two compas 
er (d) and is curved back a short distance below the nee : 
(1) and tapers uniformly throughout to the lower ¢ lon 
a sharpened point. The shorter arm (b). joins the a 
arm by an ordinary hinge joint. This arm tapers Me 
lower end, terminating in a small hook (e), and ar 
arc scale (f) which slides under the pointer. The 
marked into fifteen divisions so arranged that @ if: 
the hook (e) will be indicated in grams by the pointer. x 
spring (s) is made of gold for greater reliability, ant 
ened to the long arm by two small screws. > a 
slides freely along the shorter arm as the pressure pts 
the plate the machine is shown registering 4 ten 
of a tendril of Passiflora Pfordti. cords 
The plant at the base of the tendril is attached ee , 
an iron post (n) driven firmly in a board. The On al 
the dynamometer is driven into the board in such pos! 
7W. Pfeffer: Ber. Verhandl. K. Sachs. Gesell. Wiss. V- 638-643- " 
*Pfeffer: Die periodischen Bewegungen der Blattorgane, 1875: 
®Berichte der. deutchen bot. Gesellschaft, vi. 279- (1883). 
