246 



The Living Plant 



periment, for if a number of large seeds, such as Windsor Beans, 

 or Corn, be fixed in the most diverse possible positions (figure 87), 

 the new stems and roots will grow themselves round into the 

 up-and-down directions respectively. Furthermore, the side 



roots as they come out, and side 

 V n*^ / branches as well, assume and hold 



for a time a definite angle to the 

 same up-and-down line. That the 

 positions of these parts are taken 

 with reference to the up-and-down 

 line, and not simply in relation 

 to the main root and stem, is 

 proven by a very conclusive ex- 

 periment; for if the young plants, 

 when their parts are well formed, 

 are tipped over at an angle, or up- 



FiG. 88.— This Bean seedling was grown side down aS shoWU by OUr figure 

 for a time in this position; then it was ,„ oo\ji ii rj^i ^ 



inverted, and the new growth is reprc- (figure 88), then all ot the parts 



?redr„itLt\°:siiiriL:rd; grow as quicUy as they can into 



Still further growth. The direction of their former dlrectious. A case 



growth is obviously geotropic, not 



relative to the main root. (Copied, of aUalogOUS SOrt is found alsO 



reduced, from Sachs' Lectures.) • tvt i i ^ 



m Nature, where evergreen trees 

 that grow on irregular steep hillsides show no relation what- 

 ever to the slope of the ground, but grow as stiffly upright, 

 and with branches as truly horizontal, as if the ground were 

 quite level. These simple illustrations are typical of a well- 

 nigh universal fact about plants, — that they send their first 

 roots down and their first stems up, and their side roots and 

 side stems out at definite angles to the up-and-down direc- 

 tion, regardless of the conditions under which they originate. 

 This fact is fundamental in the economy of vegetation, for it 

 helps to explain the way in which large plants can guide their 

 growth into upright positions, and hold themselves therein, 

 and how they can spread out their branches at such definite 



