For investigating transpiration and water absorption by cut shoots. The apparatus comprises a glass cylinder stoppered at both ends, through the lower end of which is inserted a length of capillary tubing graduated in millimeters, the other end having a glass tube to which the cut shoot is attached by rubber tubing. A 2ml. syringe is provided for adjusting the air bubble position during setting up. Overall length approx. 390mm. Capillary bore 1mm