460 Prof. C. Timiriazeff. [Apr. .>0, 



If we may consider our present notions on the cosmic; il nature of 

 the process going on in the green plant an outcome of the brilliant 

 achievements of modern physical science, it is only just to try and 

 search for the first pioneers of this important notion of an intimate 

 relation between the vegetable world and the sun, as manifested in the 

 chlorophyll function. Full justice must be done to Senebier for having 

 fully conceived the idea of this wonderful connection. But before 

 arriving at this conclusion we must first give credit to a theory that is 

 too often considered as only a curious aberration of the scientific mind. 

 I mean the theory of Phlogiston. Of course, it was to be expected 

 that a theory that had a Priestley or a Cavendish for its adepts, could 

 not be so easily disposed of, and indeed we know that Helmholtz and 

 especially Professor Odling have made a generous attempt at its rehabi- 

 litation. In order to understand the real meaning of this famous 

 theory we have but to substitute for that ill-fated word the more 

 familiar expression of potential energy, and we shall see how near the 

 fundamental conceptions of this phenomenon from the point of view 

 of this theory were to those of our own time, as, for instance, in these 

 words of Senebier : " J'aime voir les corpuscules de la lumiere se corn- 

 Inner dans les corps, etc. J'aime a croire qu'ils frapperont de nouveau 

 nos yeux dans la fiamme des matieres combustibles ; il me semble lui 

 voir former les resines avec lesquelles elle a tant d'affinite", les matieres 

 huileuses pleines de sa chaleur et de sa clarte, la partie spiritueuse des 

 graines et des fruits, saturee de ses feux . . . Enfin le phlogistique, que 

 la lumiere formeroit dans les vegetaux, ne serait-il pas la source de celui 

 qui circuleroit dans les autres regnes 1 " 



When a botanist on a tour in the botanical garden of Geneva 

 stops to admire the row of marble busts of famous botanists born in 

 Geneva, Senebier in the foreground, he may feel sure that he stands at 

 the very cradle of the physiological research of the 19th century, just 

 <is in our days if he would see the place from which will surely spring 

 the physiological movement of the nascent century, he must bend his 

 steps to another botanical garden much nearer to us and salute in the 

 Jodrel Laboratory the starting point of quite a new departure on the 

 way first trodden by Senebier and Saussure. 



But in our historical retrospect we must go back another century. 

 Senebier with his characteristic candour mentions the author to whom 

 he was himself indebted for this fundamental notion of an intimate 

 connection between light/ and matter. We must look for it in a book 

 41 written " as the author informs us, " at the desire of some gentlemen 

 of the Royal Society and read at their meetings." We must open the 

 third book of Newton's * Opticks ' and read the 30th question, which 

 runs as follows : " Qiiest. 30. Are not gross bodies and light convertible 

 into one another, and may not bodies receive much of their activity 

 from the particles of light which e:iter their composition ? For all 



