70 Chapters in Modern Botany CHAP. 



Movements of Seedlings. We have seen how Darwin 

 began to believe that all plants in some degree possessed 

 the powers of movement which are conspicuously developed 

 in the climbers. To test this opinion he and his son 

 Francis began to watch and experiment with many kinds of 

 plants, and the results of their study are told in the sequel 

 to the work on Climbing Plants, a volume entitled The 

 Power of Movement in Plants (London, 1880). As before, 

 let us follow Darwin, and first of all in watching the life of 

 a seedling. 



The seed lies on the damp ground, covered perhaps 

 with leaves which have fallen from the trees. As water 

 finds its way into the seed, as the life within begins to 

 gather strength, the young root or radicle makes its appear- 

 ance. It begins at once to move round and round. But 

 its movements are influenced by gravity, and it bends 

 downwards, following a more or less spiral course towards 

 the ground. Darwin believed that " sensitiveness to gravi- 

 tation resides in the tip, which transmits some influence 

 to the adjoining parts, causing them to bend." When the 

 tip of the root reaches the soil it bores into it, aided by 

 the continued movement of the radicle, and this boring is 

 easier if some soil has fallen upon the seed and fixed it, or 

 if fine root-hairs from the top of the radicle have moored 

 the seed to the surface. Then as the radicle grows longer 

 its tip is forced into the soil. 



There it can no longer bend round and round, but it may 

 try to do so. And sometimes the tip will reach a crevice, 

 or it may be an earthworm's burrow, in which it can move 

 more freely. " When a 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 obstacle or the more resisting earth, and will 

 thus follow with unerring skill a line of least resistance." 



