CH. iiT. DOWJS'WARD GROWTH OF THE ROOTS. 



89 



dowed witli an internal structure, differing from that of 

 every other part of the plant, by which, when buried too 

 deeply, it takes the most direct line to the atmosphere 

 in which it is formed to flourish : though it would 

 puzzle our philosophy to say the agent by which this 

 growth is directed, as much as to name the agent 

 which directs the growth of the root, tap or branch. 



When the gemmules reach the air the agent 

 appears to be light. At least, when the gemmules 

 reach the air this straight upward tendency is imme- 

 diately overcome by light. These stems, after having 

 forced themselves straight upwards through eight or 

 ten inches of earth, were drawn away from the spot 

 where each emerged from the earth by light througli 

 the holes at the centre of the flower-pot. The plants Cmne-neck 



growth of 



were still crane-necked ; that is, their heads were ^^}^- 



' ' mule, to 



doubled on their stems as they came out of the seeds : ^hii^otce^f 

 and thus, while the stem of a plant whose seed has the^eSih. 

 two divisions or cotyledons is forcing its way upward, 

 its head is pointed downward, and the leaves are 

 drawn through the earth with the grain. But for the 

 contrivance of the crank or crane-neck, the leaflets, 

 owing to their branching and extending one from the 

 other, must be broken and torn to pieces by the great 

 force necessary to thrust them and the stems bodily 

 through the earth. This is a very beautiful provision. Roots grow 



The roots, on the other hand, appear to grow in ^J^^^^^^f^J^y 



through 

 the eartl 

 with ver 



length through the earth, with very little, if any, pres- 

 sure at all. This may possibly be in part owing to 



