222 HISTORY OF BOTANY 



in the regularity of the curve, as a consequence of altera- 

 tions in the conditions of the environment, and associated 

 growth with the state of turgor in the growing cells. 



The investigation of growth phenomena was greatly 

 facilitated by the use of the growth-lever, first employed 

 by Baranetski in 1879, and afterwards developed into 

 the self-recording auxanometer which you have so 

 frequently seen in operation in laboratory experiments. 

 To Sachs's papers, as also to those of Kraus, pubhshed 

 between 1865 and 1870, we owe as well the foundations 

 of our knowledge of the distribution of tensions in 

 different growing tissues, and the consequent results in 

 the maintenance of rigidity in succulent organs. 



Some Advances in Botanical Knowledge since 1900 

 I propose now to deal with a few of the many special 

 problems that have been the subject of botanical research 

 since the beginning of the twentieth century. Some 

 of these in their earher phases I have already in some 

 measure discussed, such as the evolution of the conception 

 of a phylogenetic classification of plants or the photo - 

 synthetic problem, but there are many others that I 

 have scarcely even mentioned. In summarising some 

 of these newer aspects of the science I must bear in mind, 

 however, the warning uttered by Sir Walter Raleigh, 

 who, in his History of the World, apologises for not writing 

 the history of his own time—" which would," he says, 

 " have been more pleasing to the reader "—on the ground 

 that " whosoever in writing a modern history shall follow 

 truth too near the heels, it may haply strike out his 

 teeth." Having no desire to suffer this facial injury 

 I do not propose to offer you a complete statement on 

 any one of these subjects ; all I can do is to select some 

 of what appear to me to be the most important Hues of 

 development of the science, leaving the lesser bypaths 

 for your own exploration. 



