ABSTRACT
The plant, the growth in length of which is to be studied, is placed under a stand of this kind, and a pin is passed through the apex of the stem; then a thread is fastened to the pin and is carried over a small pulley, while to the other end a small weight is attached. The arrangement of the present piece of apparatus, made by Stohrer, is somewhat complicated. There are finally two large glass bottles, to which the author direct an attention, used by Professor Sachs of Wurzberg, in the important investigations as to the parts of the spectrum to which different kinds of physiological work in plants are to be attributed. In point of fact, the light belonging to the red end of the spectrum, including the red and yellow rays, does nearly the whole work, and the blue light is comparatively inactive as regards vegetative work.
