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TEXTBOOK OF PLANT PHYSIOLOGY 



distance covered by the extremity of the plant is determined (Fig. 

 105). Knowing the magnification of the microscope, it is easy to 

 , calculate the growth increase. It is possible to use a self-recording 

 apparatus, the so-called auxograph in which, by means of pulleys 

 and wheels, changes in the position of the tip of a plant are recorded 

 on an enlarged scale on the surface of a revolving smoked paper 



Fig. 105. — Measurement of growth by means of a horizontal microscope {after 



Molisch). 



cylinder (Fig. 106). Auxographs usually give an enlargement of 

 twenty to forty times. From such records one can read alterations 

 in growth, occurring in the course of half an hour or an hour. 

 Recently, however, the Indian scientist Bose has constructed an 

 apparatus, the crescograph, which gives enlargements of 1,000 and 

 even 10,000 times. This apparatus allows one to record the prog- 

 ress of growth not only by minutes but even by seconds. 



Often it is important to follow the growth of certain organs 

 instead of that of the whole plant. In such cases, Sachs' method of 



