MOVEMENTS OF SEEDLINGS. 41 



importance to the plant ; for we have seen that 

 when little bits of card-like paper, and of very 

 thin paper, were cemented on opposite sides of the 

 tip, the whole growing part of the radicle was 

 excited to bend away from the side bearing the 

 card, or more resisting substance, towards the side 

 bearing the thin paper. 1 We may therefore feel 

 almost sure that when the tip encounters a stone 

 or other obstacle in the ground, or even earth 

 more compact on one side than the other, the root 

 will bend away as much as it can from the obsta- 

 cle or the more resisting earth, and will thus follow 

 with unerring skill a line of least resistance . . ." 2 

 (Fig. 6). 



1 "The accompanying figures of four germinating seeds (Fig. 6) 

 show, firstly, a radicle (A), the apex of which has become so much 

 bent away from the attached square as to form a hook; secondly (B), 

 a hook converted through the continued irritation of the card, aided 

 perhaps by geotropism, into an almost complete circle or loop. The 

 tip in the act of forming a loop generally rubs against the upper part 

 of the radicle, and pushes off the attached square ; the loop then con- 

 tracts or closes, but never disappears, and the apex afterwards grows 

 vertically downwards, being no longer irritated by any attached object. 

 This frequently occurred, and is represented at (C). ... In another 

 case, shown at (D), the apex in making a second turn or spire, passed 

 through the first loop, which was at first widely open, and in doing so 

 knocked off the card; it then grew perpendicularly downwards, and 

 thus tied itself into a knot, which soon became tight." "Power of 

 Movement in Plants," p. 178. The conclusions drawn from these 

 experiments are not accepted by many students, and the experiments 

 themselves are criticised, as containing sources of error. 



2 p. 549. 



