Page:The Modern Review (July-December 1925).pdf/743

716 the response of all plants, sensitive and ordinary, under external and internal stimuli.

Recorder for the Ascent of Sap. No apparatus has hitherto been available for the detection or measurement of the movement of sap in the interior of the plant. The problem has been completely solved by the invention of two independent methods of record, mechanical and electrical.

The Transpirograph measures the rate of transpiration current and has enabled the determination of the water transpired by a single stoma of the leaf.

The Photosynthetic Recorder automatically inscribes, on a moving drum, the rate of carbon-assimilation by plants. It is so extremely sensitive that the formation of carbohydrate as minute as a millionth of a gram can be detected by its means. One of the most important results discovered is the extraordinary increase in the power of assimilation. produced by infinitesimal traces of certain stimulating agents.

The Crescograph was invented to measure instantly, the imperceptible rate of growth, and its induced variations under chemical and electrical stimulants. This device enables the discovery of substances, traces of which are of extraordinary efficacy in increasing the growth of plants on which the food supply of the world depends.

The Magnetic Crescograph enables movements, which are beyond the highest magnifying powers of the microscope, to be detected and recorded; the magnification produced may be carried to a hundred million times. This invention has opened out possibilities for great advance in various branches of science.