A potometer measures how factors such as light, temperature, humidity, light intensity and wind will affect the rate of transpiration. The main type of potometer is the 'bubble' potometer shown in Figure Figure 6.
Physicians recommended against the practice because they did not want medicines associated with punishment. A heavy dose of castor oil could be used as a humiliating punishment for adults, especially political dissenters. Colonial officials used it in the British Raj (India) to deal with recalcitrant servants. Belgian military officials prescribed heavy doses of castor oil in Belgian Congo as a punishment for being too sick to work.
Castor oil. Castor oil is a vegetable oil obtained by pressing the seeds of the castor oil plant (Ricinus communis). The common name castor oil, from which the plant gets its name, probably comes from its use as a replacement for castoreum, a perfume base made from the dried perineal glands of the beaver (castor in Latin).