Reverend Stephen Hales

You may not have heard of him but gardeners owe a lot to the Reverend Stephen Hales. He is the father of plant physiology, and modern biology is built on many of his observations and experiments on living plants. Born in 1677, he was the curate of Teddington Church from 1709 to his death in 1761. Among his many discoveries he found that sap flows from roots to leaves (i.e., transpiration) and that leaves need light to grow and they absorb air (i.e., photosynthesis). His paper in 1719 to the Royal Society was ‘Upon the Effect of ye Sun’s warmth on raising ye Sap in trees’. Until his work on measuring sap pressure, velocity and circulation (inventing a trough to collect gases and gauges to measure pressure), it was thought that sap circulation was similar to that of blood in the body.

Earlier, he had studied blood pressure in horses, and pulse rates and the capacity of the heart to pump blood in variously sized animals. He invented a ventilator to rid hospitals, ships and mines of noxious gases. He sought ways of distilling pure water from sea water, of preserving foods for long ocean voyages and in tropical climates, of measuring earthquakes and preventing forest fires and he invented the medical forceps.

And in addition to tending to his flock’s spiritual needs, he checked the limescale in their teapots, told them to put an upturned teacup in pies to stop juice overflowing, and painted tops of footpath posts so they could find their way home in the dark. What a man!

(Thanks to Rob Monk, a frequent contributor to the newsletter, for this information.)