1896] LABORATORY APPARATUS IN VEGETABLE PHYSIOLOGY 465 
usually necessary to put weights of a few milligrams upon the 
carriage in order to make the machine run uniformly. 
Many trials have been made to secure a satisfactory thread 
forthe pulleys. The material found to work best is sewing silk 
A sufficient length is taken and untwisted, and only a part of 
one strand used. All. attempts to secure a smoother thread by 
employing wax of some sort have met with indifferent success, 
and finally have been abandoned. The thread which leads from 
the plant to the small pulley is carried through a bent glass tube 
which offers but the slightest possible friction, and obviates the 
necessity of placing the plant directly underneath. 
To adjust the apparatus the thread from the needle carriage 
is threaded through an opening in the rim of the large pulley 
wheel and fastened ina slit, the carriage remaining at the bottom 
of the guides. A thread from the plant is then passed through 
the glass rod and once around one of the smaller pulley wheels, 
and after the pulley is turned so that the needle carriage is at 
the top of the guides, the thread is fastened in a slit at the side 
of the small wheel. The carriage is now weighted enough to 
keep the threads barely straight. The recording part is next 
brought into place, and set so that the point of the needle will 
make a mark as the blackened rods pass it. To have the record- 
NY rods parallel to the path of the needle the apparatus should 
~ Set upon a level surface, preferably on a piece of plate glass. 
As the plant grows the needle descends at a multiplied rate, and 
“Wes the record on the blackened rods. 
here are no hanging weights, and no unnecessary pull upon 
; Plant in this machine. The needle carriage and its riders 
_ “stitute the sole weight for turning the pulley. As the plant 
_ "ws the thread which leads from it is wound up on the small 
Pulley Wheel, and the thread attached to the needle carriage is 
“Wound from the large wheel, permitting the needle to descend. 
he small excess of weight permissible above that necessary 
es vetcome the friction of the machine, in order not to influ- 
, me Perceptibly the growth of the organ under observation, 
it imperative that the movable parts of the machine 
to 9 
