1 882.] On the Compass Plant. 635 



dencies, plainly bring out the conclusion * that the power which 

 leaves have of placing themselves at right angles to the incident 



to regulate or govern the action of other external forces, such 

 as epinasty.' " 



Professor Bessey, in his recent admirable work on botany, page 

 193, says: "The explanation for heliotropism which is com- 

 monly given, is that the light retards the growth on the illumi- 

 nated side, while the shaded side elongates, resulting in a tension 

 which necessarily produces a curvature." 



This is the most plausible statement we have seen, but we are 

 not informed how far it is founded on any actual experiment. It 

 is satisfactory that Mr. Darwin has undertaken the task in such a 

 careful and systematic manner. It is an interesting field of ob- 

 servation and worthy of being thoroughly examined by different 

 persons and in different localities. 



LIST OF PAPERS ON THE COMPASS PLANT, ETC. 

 Bf.vja.min Ai.vord, U. S. Army.— Proceedings of National Institute, Washington, 



Professor 



•ney._ Amer: 



Hknxei 



turalist for March, 1871, p. I. 



T, Lecturer on Botany at St. The 



.mas 





Eng.- 



-Nature for ] 





[877, p. 298, with figure of the planl 







Dr. George 





r,of St. 







Adv 





of Sc 



ience, St. Louis, Aug., 1878. 









Professor C. E. Bessey. 



— Amei 



:i<:a» Natural! 



st for August, 1877, p. 



4 So. 





Botany. 



Henry Hoi 



n of leaf m^ 



U;''u 



, N. Y., 1S80, 



pages 103, 157, 515, > 



nth 



figures of 



D R- Asa Gr 



AY.— Ed. Of 



1880 of 



Botany of N 



orthern U. S. 







Americ: 



m Journal of 



Science for March, 



1882, page 245. On 



Fra 



ncis Dar- 





paper in Join 







Society, No. 112, Vol 





PP- 42C- 





unc iSSi.on 



"The 



power possess 



ed by leaves of placing 



■ &v 



nselves at 



Sl R Joseph D. Hooker and Dr. Asa Gra 



" W - G. F.,» or PaorESSOR W. G. FARL< 



Journal of Science for February, IV 

 'he Jen. Zeitschrift, Germany. 



