Letter from W T [William Turner] Thiselton-Dyer, The Ferns, Wicombe, Gloucester, to [Joseph] Larmor He thinks that the problem is to maintain a continuous flow of water at the top of a tree, one hundred feet or more in height, taking into account mechanical principles and solar energy. He discusses theories of 'pumping action' by Herbert Spencer, by [Alfred James] Ewart, and by [Henry Horatio] Dixon. He considers 'osmotic suck' and the complexity of plants in respect of physical explanations. He notes a conversation he had with Larmor on the cause of osmotic pressure, which Larmor said was the kinetic energy of the molecules, but Thiselton-Dyer does not consider this to be an explanation.. 13 January 1907