324 Life and Immortality. 



some plants, there can be no doubt that it is it that affords 

 the radicle some slight assistance in penetrating the ground. 

 But whether or not a radicle, when surrounded by softened 

 earth, is aided in making a passage for itself by circumnu- 

 tating, one thing is certain, that is, that this movement, by 

 guiding the radicle along a line of least resistance, can hardly 

 fail to be of high importance. Should, however, a radicle in 

 its downward growth break obliquely into any crevice, or an 

 opening left by a decayed root, or one made by the larva of 

 an insect, and more especially by worms, the circumnutating 

 movement of the tip will materially aid it in following such 

 open passages. Not only our own observation, but also those 

 of such eminent authorities as Darwin and Hensen, conclu- 

 sively show that roots commonly run down the old burrows 

 of worms. 



But radicles of seedlings, as well as those of more vigor- 

 ous plants, would pass over stones, roots and other obstacles, 

 which they must necessarily encounter in the soil. This 

 they are abundantly able to do, for they are exceedingly 

 sensitive just above their apices, and bend like a tendril 

 towards the touching object. When, however, one side of 

 the apex is pressed by any object, the growing part bends 

 away from that object, and this seems a beautiful adaptation 

 for avoiding obstacles in the soil, and for following the lines 

 of least resistance. 



So feeble is the circumnutating movement of the terminal 

 growing part, both of the primary and secondary radicles, 

 that it can assist them but little in penetrating the ground, 

 excepting when the superficial layer is very soft and moist. 

 But it must aid them materially when they chance to break 

 obliquely into cracks, or into burrows that have been made 

 by earth-worms or larvae. Moreover, combined as it is with 

 the sensitiveness of the tip of the radicle to contact, it can 

 hardly fail to be of the highest importance, for as the tip is 

 always endeavoring to bend to all sides, it will press on all 

 sides, and will thus be able to discriminate between the 



