The daily morning journal and courier., 1900-08-23

not easy to explain the relation be-
 tween the two acts. These purposeful
 activities of the plant are called trop-
 isms There are a number of them, ana
 they are of the greatest importance for
 the success of the plant as an individ-
 ual. By means of geotropism, the plant grows root down and leaves up in the air in response to the force of gravity;
 but If it is planted on a revolving wheel, where centrifugal force will annihilate gravity, it may be made to grow, in de- fiance of plant tenets, with its root in the air and its leaves down in the ground. Certain plants have free nov ing forms, called plasmodia, that will work their way along against current of water; the network of flores that makes up certain moulds grow in the direction of current, and roots of plants, are also affected by the direc- tion of a current of water coming in contact with them.
 | There are several tropsms to guide the seemingly insensate root in it's blind wanderings through the soil. Geotropoism heliotropism galvano- tropisnl, the responses to gravity light and electric currents, are localized in the root tip alone, and direct its growth down into the earth and away from light and electric currents when there are any. Active growth Of the root takes place just above the tip, and In this zone are localized the centers of perception for hydrotropism, ther- motropis.n, acrotropism, by means of which the root is guided to moisture and away from heat and the air ! Juel experimented on seedlings to find out whether the laws governing their growth compelled them to turn against q current or to grow in the same direction. He planted the seeds on pieces of cotls placed on wheel In such a way that they projected into the water and allowed 1t to flow freely around the roots as they developed. The water was kept at constant tempera- ture (20) degrees CD and the apparatus was so arranged that the rapidity of the current could be varied at will. By fastening the seeds in q definite posi- tion, the amount of growth in any di- rection could be accurately determined, and as different parts of the root vary in function, he also tried to find out in which part the susceptibility to cur rent of water was localized.
 With slow moving currents responses were uncertain, and no definite results were obtained, but he succeeded with more rapid currents. Tn one set of In- dian corn seedlings, the tip was cut off from part of the roots for about a mill limetre and half, while the others were left perfect The ,ninjured roots turned against the current through an angle Of from 30 to 65 degrees in twen- ty-four hours, and those with root tips cut off turned from to 30 degrees in the same length of time. Ten other sets, exposed to a more rapid current, turned through angles of from 30 to 70 degrees in twenty-two hours, with from 30 to 40 degrees for those with root tips cut off.
 On account of the turning of the roots from which the tips had been removed, Juel concludes that rheotropism, or the power to turn in response to the stirnu- Jus given by a current of water, must be located in the growing zone; and from the direction of the turning it is evident that there is something in the nature of these roots that enables them to perceive the direction of the cur rent and to place themselves in a defi- nite position with regard to it-The Re- view oe Reviews.