CH. nr. DOWNWARD GROWTH OF THE ROOTS. 87 



of all the seeds, without a single exception, came 

 straight down into the air, and ceased to grow when 

 the ends in the air were from a quarter of an inch to 

 an inch long. None ever turned up again. The 

 plants, however, threw out branch-roots from their 

 necks, fixed them upward in the earth, and continued 

 to grow. Those parts of the roots which remained 

 alive exposed to air and light for six weeks and up- 

 wards turned green, as did the cotyledons themselves ; 

 that is, the two divisions of the seed. 



At the same time, I took some horse-chestnut 

 seeds, v/hose first or tap-roots had already begun to 

 grow, and placed them so that these tap-roots pointed 

 upward into the earth in the inverted fiower-pot, and 

 the seeds touched the wire below. In all the cases 

 the roots immediately turned straight down and came 

 through the wire into the air. The gemmules or 

 heads of five also came down, and, on cutting away 

 the wire, all five grew horizontally to the light at the 

 window, and then grew diagonally upward and to the 

 light. The gemmules or heads of the rest grew up- 

 ward through about 8| inches of earth, were drawn 

 by the light with unerring precision through the hole 

 of the flower-potj and one through an accidental hole 

 of about a quarter of an inch in diameter. They then 

 turned short towards the light at the window. 



In November, on taking the flower-pot off, I found 

 that branch-roots had passed over the top of the ball 

 of earth, 8^ inches high. I replaced the flower-pot 



