464 BOTANICAL GAZETTE [ DECEMBER 
The object has been to secure a piece of apparatus that will 
be simple, easily adjusted, giving so small an amount of tension 
to the tender part of the plant being studied as to be inapprecia- 
ble, record with accuracy, and withal comparatively inexpensive. 
The apparatus (f/. XX/)V’) stands about 45°™ high, and con- 
sists of two separate parts. The recording part supports a clock 
(either a twenty-four hour or eight-day clock) above, with its 
dial uppermost. To the lower end of the shaft which carries 
the minute hand is attached a frame supporting two glass rods, 
each 30™ long. These rods are blackened by holding them 
over burning camphor gum, and receive transverse marks from a 
descending needle as they revolve once an hour. 
Blackened glass rods in place of a revolving drum were first 
used on this apparatus, so far as the writer knows. They are 
very easily handled, and permanent records are readily secured 
by making blue prints, or the rods themselves can be kept. The 
principal value of two rods, rather than one, is to act as a con- 
trol or duplication of the record, although separated by a half- 
hour interval. 
The other part of the apparatus carries the multiplying pul- 
ley and needle. The pulley is made of aluminum for sake of 
lightness, and runs on carefully adjusted parallel bearings. 
There are one large and two small wheels upon the pulley shaft, 
permitting a magnification of the amount of growth either eight 
or fifteen times. 
In the earlier machines, shown at the Madison meeting of 
the American Association for the Advancement of Science im 
1893,* and illustrated in plate. XXIV, the recording needle was 4 
bristle adjusted in an aluminum holder, which slid upon a verti- 
cal glass rod, a second glass rod acting as a guide. This was 
found to be too heavy and clumsy, and has been replaced 2 dig 
needle of fine brass wire attached to a skeleton carriage of similar 
Wire, running upon two parallel tight wires in place of the glass 
rods. The needle and carriage together are barely heavy enough 
to straighten the slender thread used to suspend them, and it 1% 
*See Bor. Gaz. 18: 348. 1893. 
