CHARACTER AND RATE OF GROWTH IN STEMS 215 
less it is so slow, except in a few cases, that it is imperceptible 
to the unaided eye; and, therefore, to directly observe it, the 
growing organ must be watched under the microscope. How- 
ever, in measuring growth in large organs, such as stems, leaves, 
and roots, other methods that are more convenient are usually 
employed. Thus by marking a stem into segments as shown 
Fic. 196.—Stem of a seedling marked to show the regions of most elongation. 
A, stem just after marking. 8B, stem after a few hours growth. 
in Figure 196 and observing the spread of the marks apart, 
one can easily determine what part of the stem is most active 
in elongation. Special kinds of apparatus run by clockwork, 
one of which is known as the auxograph (meaning “growth 
writer’) and another as auzanometer (meaning “growth meas- 
urer’’), have been so devised that the rate and fluctuations 
in growth are recorded by a pen which indicates the character of 
the growth throughout a considerable period by curvatures in the 
