AUX'ANOM'ETER (Gk. atVveui, auxanein, to make large, to increase + I.Lerpov, victron, measure). A device for observing or recording the growth of plants during intervals too short for direct measurement. The simpler forms of the auxanometer consist of a very light, balanced lever, whose fulcrum is so placed that the length of the long arm is a multiple of the length of the short arm. To the latter a thread from the growing plant is attached. The growth is thus magnified in the ratio of the long arm to the short, usually 10 to 20 times. The long arm traverses a graduated arc, from which its movement may be read, or it may be so placed as to trace its path on a moving smoked surface.
The more elaborate forms consist of a wheel with fine bearings and an accurately balanced rim, about 20 centimeters in diameter, grooved to carry a thread. The same hub has a smaller wheel with a grooved rim, whose diameter is cine-tenth or one-twentieth that of the larger. The wheel is supported on a suitable stand, and the plant to be studied is set beneath it. To the plant a silk thread is attached, carried around the small wheel, and weighted just enough to take up the slack by rotating the hub as the plant grows upward. Over the rim of the large
wheel a similar thread is passed, carrying on one end a marker, and on the other at counter poise. The recording apparatus consists of a cylinder driven by clockwork. and carrying smoked paper. the marker hearing against the smoked surface. The cylinder may be rotated continuously by clockwork. In that case, once in 12 hours the marker describes a spiral line of steep or of low pitch, according to the rate of growth. The best forms, however, release the cylinder by means of an electromagnet, the cir cuit being closed by a clock, at intervals, when the cylinder is allowed to rotate a short distance (2 to 4 millimeters). This gives a broken line, whose vertical parts represent the growth during the intervals of rotation, and the horizontal parts the distance through which the cylinder turned. A great variety of forms embodying the fore going principles have been devised and described.