380 



PHYSIOLOGY OF GROWTH. 



the paper uniformly with a moderately moist sponge, gum both 

 long edges, and roll the cylinder over the paper. When the paper 

 has become dry, we pass the cylinder to and fro over a large, broad 

 turpentine flame so as to coat it uniformly with soot. When the 

 auxanonaeter is in motion with the drum placed excentrically, the 

 indicator, z, set in movement by the growth of the plant, comes 

 in contact for a time every hour with the rotating' cylinder, and 

 removes the soot from its surface at the places of contact. The 

 lines thus produced are fixed by passing the paper after removal 

 from the drum through an alcoholic solution of colophonium, and 

 drying. If we measure the distance between the lines, we obtain 

 a direct measure of the growth movement. Sachs has so fully de- 

 scribed the whole method of procedure, and the sources of error 

 which it presents, that we must refer for details to his cited work, 

 especially pp. 116, 118, and 119. 



The self-registering auxanonaeter may be used for many re- 

 searches on growth. It is especially indispensable when it is 

 desired to obtain exact information as to the character of the daily 

 period of growth of internodes (see further below). 



For accurate measurements of very small growth movements of 

 vertically growing structures, a horizontal microscope (or tele- 

 scope) is essential. The Quincke-Pfeffer apparatus represented in 

 Fig. 125 is very suitable It may be obtained from Albrecht, in 

 Tubingen, at a price of 110 marks. 

 The tube of the microscope is 

 focussed on the object under in- 

 vestigation by means of the screw, t. 

 The pillar, s, moving in the tube h, 

 serves for coarse adjustment in the 

 vertical direction, while the milli- 

 metre screw, m, serves for fine ad- 

 justment, and for re-focussing when 

 the image of the object has run 

 through the scale of the ocular 

 micrometer. By means of this 

 accurately cut screw we can at once, 

 as with a cathetometer, measure the FlG - 125. Horizontal measuring 



-,.,,, . microscope. (After Pfeffer.) 



distance between marks not simul- 

 taneously included in the field of view. For example, one revolu- 

 tion of the milled head may correspond with 0792 mm., and J 

 divisions can be accurately read on the scale below it, which is 



