78 



GROWTH OF SEEDLINGS 



To the pulley a wire index is fastened. A cord is tied 

 about the stem of a plant very near to the terminal bud. 



This cord passes over the pulley 

 and is held taut by a weight 

 which is just heavy enough to 

 move the pointer. Set the 

 pointer at zero. 



As the stem elongates the 

 weight will drop, pulling the 

 pointer upward as the pulley 

 revolves. If properly adjusted, 

 a very slight growth of stem 

 will be indicated by a rise in 



\" ' fet i the pointer. 



\ Query. What effect has fer- 

 tility of soil on growth? What 



FIG. 24. Auxanometer. , 



enect does water have on growth r 



How do plants of desert regions compare in size with those 

 of moist regions ? Why are mountain plants diminutive in 

 size, while lowland plants of the same kind grow to greater 

 size? 



