346 



The Living Plant 



and as can easily be effected by experiment, then growth ceases; 



and indeed death ensues unless the supply be admitted again. 



Furthermore, in the chemical reactions of growth, some waste 



by-products are formed, of which a part are dropped with the 



bark and the leaves, a part 

 are stored in out of the way 

 cells, and a part are appar- 

 ently excreted into the soil, 

 where they act poisonously, 

 and produce economic and 

 ecological consequences al- 

 ready described. 



A notable feature of growth 

 is its accompaniment by a 

 number of different move- 

 ments. Many of these are 

 clearly adjustive of the parts 

 to the particular conditions 

 of light, moisture, and so forth 

 prevailing in the immediate 



Fig. 132.— An arrangement (ahout one-sixth environment, and aS SUCh 

 the true size), for the study of circumnuta- -i i " ] ] 1 r1 



tion, using a method described in the text. il^Ve DeCU COnSlCiereQ aU'Caay 

 The glass filament and paper triangle, some- J^^ q^^j. chapter On Irritability, 

 what exaggerated for visibility in the draw- ^ "^ ' 



ing, may be seen near the center of the while they wiU alsO reCcive 



further mention in suitable 

 places in the chapter that follows. There is, however, one move- 

 ment of which the description belongs here, since it is an inciden- 

 tal accompaniment of all growth. It is that which was named by 

 Darwin, its discoverer, circumnutation. So slow is it, ordinarily, 

 however, that special methods are needed to render it apparent. 

 If one takes some young seedling, such as Radish or Corn, attaches 

 alongside its tip by harmless cement a slender projecting glass fila- 

 ment, places black reference marks on the end of the filament and 

 on a bit of white paper at its base, and then supports a pane of 



