54 CIRCUMNUTATION OF SEEDLINGS. CHAP. I. 



the windows was a little more illuminated than the opposite 

 side; and during the first morning the stem travelled to a 

 greater distance in this direction (to the left in the figure) than 

 it did afterwards when the box was completely protected from 

 light 



Fig. 40. 



Quercus (American sp.) : circumnutation of young stem, traced on hori- 

 zontal glass, from 12.50 P.M. Feb. 22nd to 12.50P.M. 24th. Movement 

 of bead greatly magnified at first, but slightly towards the close of the 

 observations about 10 times on an average. 



Quercus rdbur. Observations were made only on the move- 

 ments of the radicles from germinating acorns, which were allowed 

 to grow downwards in the manner previously described, over 

 plates of smoked glass, inclined at angles between 65 and 69 

 to the horizon. In four cases the tracks left were almost straight, 

 but the tips had pressed sometimes with more and sometimes 

 with less force on the glass, as shown by the varying thickness 

 of the tracks and by little bridges of soot left across them. 

 In the fifth case the track was slightly serpentine, that is, the 

 tip had moved a little from side to side. In the sixth case 

 (Fig. 41, A) it was plainly serpentine, and the tip had pressed 

 almost equably on the glass in its whole course. In the seventh 

 case (B) the tip had moved both laterally and had pressed 



