14'^ TEANSACTIONS OF THE ILLINOIS 



With such ilhistrative examples, easily verified by any one at 

 any time, we must admit that in ordinary plants, under ordinary 

 circumstances, the root system is enormously developed, and merits, 

 though hid away from sight, careful study and thoughtful treatment. 



Movements of Boots. — It is popularly supposed that plants are 

 distinguished from animals in not having the power of motion. Any 

 one who has studied the lower, microscopical forms of plants knows 

 that no distinction of this kind can be made, for many of these 

 simplest of vegetable forms move as spontaneously and freely as any 

 animals ever do. These plants are aquatic, and swim rapidly through 

 the water by the vibration of hair-like appendages. None have lo- 

 comotive organs similar to legs or wings of animals, but when 

 closer studied, it is found that all plants possess the innate and self- 

 controlled power of movement. This is conspicuous in the stems of 

 twining plants. These wind about a support by an inherent force 

 which carries the free end of the vine spirally about a stake. 

 Arriving at the top the growing end reaches upward and outward, 

 and, at the same time, swings in its own special direction around, 

 sweeping a circle whose radius constantly increases by the elongation 

 of the growing shoot. In this way the end of climbing vines, like 

 hops or morning glories, may traverse a circle three to five feet in 

 diameter, and complete the circuit in from one and a half to two and 

 a half hours. We readily see the use of this swinging movement 

 in the vine, for, as the growing end thus reaches out in every direc- 

 tion, new supports may be found, and the possibility afforded of 

 higher ascent. Nor is the search altogether haphazard, for such 

 climbers always reach further on the side from which least light 

 comes; thus a post, or other object, by intercepting the rays of light, 

 is always likely to be gained by the vine. The opening and closing 

 of flowers and what is called the sleep of leaves furnish other illus- 

 trations of these self-caused movements in plants. 



Now it has been ascertained that the growing tips of all roots, 

 when free to do so, continually move so as to describe some form 

 of an ellipse. As the growing end advances, at the same time a 

 spiral figure is produced by the path of the moving tip. Of course 

 such movements cannot take place when the roots closely press upon 

 the soil upon all sides. But in germinating seeds not buried in the 

 soil, and wherever in the earth a cavity is reached by growing roots, 

 such movements always occur. The extent of the lateral swing is 

 always very small, and takes place only in the terminal inch, or two 

 inches at most, of the root. Here again the sideward reach in a 

 given direction is modified in a curious manner. In primary roots 

 — the main root from the seed — if the axis is horizontal the down- 

 Avard swing is greater than the upward, and the tip therefore gradu- 

 ally bends toward the center of the earth. When at last a vertical 

 direction is attained, the swing from the center becomes equal and 

 the direction is retained. What causes the leading stems of plants 



