336 ' BOTANY. [ch. xvir. 



a place among the canons of orthodox physiology. The 

 book has been treated by Professor Sachs with a few words 

 of professorial contempt ; and by Professor Wiesner it has 

 been honoured by careful and generously expressed criti- 

 cism. 



Mr. Thiselton Dyer * has well said : " Whether this mas- 

 terly conception of the unity of what has hitherto seemed a 

 chaos of unrelated phenomena will be sustained, time alone 

 will show. But no one can doubt the importance of what 

 Mr. Darwin has done, in showing that for the future the 

 phenomena of plant movement can and indeed must be 

 studied from a single point of view." 



The work was begun in the summer of 1877, after the 

 publication of Different Forms of Flowers, and by the au- 

 tumn his enthusiasm for the subject was thoroughly estab- 

 lished, and he wrote to Mr. Dyer : " I am all on fire at the 

 work." At this time he was studying the movements of 

 cotyledons, in which the sleep of plants is to be observed in 

 its simplest form ; in the following spring he was trying to 

 discover what useful purpose these sleep-movements could 

 serve, and wrote to Sir Joseph Hooker (March 25th, 1878): 



" I think we have proved that the sleep of plants is to 

 lessen the injury to the leaves from radiation. This has 

 interested me much, and has cost us great labour, as it has 

 been a problem since the time of Linnaeus. But we have 

 killed or badly injured a multitude of plants. N.B. Oxalis 

 carnosa was most valuable, but last night was killed." 



The book was published on November 6, 1880, and 1500 

 copies were disposed of at Mr. Murray's sale. With regard 

 to it he wrote to Sir J. D. Hooker (November 23) : 



"Your note has pleased me much, for I did not expect 

 that you would have had time to read any of it. Read the 

 last chapter, and you will know the whole result, but without 

 the evidence. The case, however, of radicles bending after 

 exposure for an hour to geotropism, with their tips (or brains) 

 cut off is, I think worth your reading (bottom of p. 525) ; 

 it astounded me. But I will bother you no more about my 

 book. The sensitiveness of seedlings to light is marvellous." 



To another friend, Mr. Thiselton Dyer, he wrote (No- 

 vember 28, 1880) : 



" Very many thanks for your most kind note, but you 

 think too highly of our work, not but what this is very 



* Charles Darwin, Nature Series, p. 41. 



