CHAP. I. 



PHALARIS. 



63 



Fig. 49. 



action of light ; and if any enters even temporarily on one side, 



they merely bend to this side in slightly zigzag lines. Of the three 



tracings one alone (Fig. 49) is here given. Had the observations 



been more frequent during the 12 h. 



two oval figures would have been 



described with their longer axes at 



right angles to one another. The 



actual amount of movement of the 



apex from side to side was about 



3 of an inch. The figures described 



by the other two seedlings resembled 



to a certain extent the one here 



given. 



A seedling which had just broken 

 through' the ground and projected 

 only -^th of an inch above the 

 surface, was next observed in the 

 same manner as before. It was 

 necessary to clear away the earth 

 all round the seedling to a little 

 depth in order to place a mark 



beneath the apex. The figure (Fig. 50) shows that the apex 

 moved to one side, but changed its course ten times in the 

 course of the ten hours of observa- 

 tion ; so that there can be no doubt 

 about its circumnutation. The 

 cause of the general movement 

 in one direction could hardly be 

 attributed to the entrance of 

 lateral light, as this was carefully 

 guarded against ; and we suppose 

 it was in some manner connected 

 with the removal of the earth 

 round the little seedling. 



Lastly, the soil in the same pot 

 was searched with the aid of a 

 lens, and the white knife-like apex 

 of a seedling was found on an exact 

 level with that of the surrounding 



surface. The soil was removed all round the apex to the depth 

 of a quarter of an inch, the seed itself remaining covered. The 

 pot, protected from lateral light, was placed under the micro- 

 4 



mark placed below the apex, 

 traced on a horizontal glass, 

 from 8.35 A.M. Nov. 26th to 

 8.45A.M. 27th. Movement of 

 apex magnified 7 times, here 

 reduced to one-half scale. 



Fig. 50. 



Phalaris Canariensis : circumnu- 

 tation of a very young coty- 

 ledon, with a mark placed 

 below the apex, traced on a 

 horizontal glass, from 11.37 

 A.M. to 9.30 P.M. Dec. 13th. 

 Movement of apex greatly 

 magnified, here reduced to 

 one-fourth of original scale. 



