As regards the action of light on plants, he suggests (p. 327) that "by freely entering the expanded surfaces of leaves and flowers" light may "contribute much to the ennobling principles of vegetation." He goes on to quote Newton (_Opticks, query 30_): "The change of bodies into light, and of light into bodies is very conformable to the course of nature, which seems delighted with transformations." It is a problem for the antiquary to determine whether or no Swift took from Newton the idea of bottling and recapturing sunshine as practised by the philosopher of Lagado. He could hardly have got it from Hales since _Gulliver's Travels_ was published in 1726, a year before _Vegetable Staticks_. Timiriazeff, in his Croonian Lecture[51], was the first to see the connexion between photosynthesis and the Lagado research. Nevertheless Hales is not quite consistent about the action of light; thus (p. 351) he speaks of the dull light in a closely planted wood as checking the perspiration of the lower branches so that "drawing little nourishment, they perish." This is doubtless one effect of bad illumination under the above-named conditions, but the check to photosynthesis is a more serious result. In his final remarks on vegetation (p. 375) Hales says in relation to greenhouses, "it is certainly of as great importance to the life of the plants to discharge that infected rancid air by the admission of fresh, as it is to defend them from the extream cold of the outward air." This idea of ventilating greenhouses he carried out in a plant house designed by him for the Dowager Princess of Wales, in which warm fresh air was admitted. The house in question was built in 1761 in the Princess's garden at Kew, which afterwards became what we now know as Kew Gardens. The site of Hales' greenhouse, which was only pulled down in 1861, is marked by a big _Wistaria_ which formerly grew on the greenhouse wall. It should be recorded that Sir W. Thiselton-Dyer[52] planned a similar arrangement independently of Hales, and found it produced a marked improvement of the well-being of the plants. It is an illuminating fact that though Hales must have known Malpighi's theory of the function of leaves (which was broadly speaking the same as his own), he does not as far as I know refer to it. In his preface, p. ii, he regrets that Malpighi and Grew, whose anatomical knowledge he appreciated, had not "fortuned to have fallen into this _statical_[53] way of inquiry." I believe he means an inquiry of an experimental nature, and I think it was because Malpighi's theory was dependent on analogy rather than on ascertained facts, that it influenced Hales so little.