Ch. IV, 7] 



GROWTH OF PLANTS 



161 



products of respiration, both carbon dioxide and heat are 

 released in growth. 



All of the phenomena here described in connection with 

 stems appear also in leaves, roots, and other parts, as shown 

 by use of a suitably 

 modified auxograph, or 

 by the measuring mi- 

 croscope. All parts are 

 found to exhibit the 

 grand period, and the 

 fluctuations in relation 

 to the weather; and 

 the only appreciable 

 differences in their 

 modes of growth are 

 associated with their 

 differences in construc- 

 tion. Stems grow by 

 the progressive elonga- 



Fig. 113. — The place of expansion in 

 growth of a typical leaf of English Ivy, as 

 shown by the spread of the marks evenly 

 made on the small leaf at the right ; X £. 



tion of their internodes, which, forming in the bud, go 

 through their grand periods in succession ; and thus is pro- 

 duced the familiar appearance 

 which has been compared with 

 the opening out of the joints of a 

 telescope (Fig. 112). The leaves, 

 quite differently, expand pretty 

 evenly throughout their structure 

 (Fig. 113), going each through its 

 grand period, as do flowers and 

 fruits. The roots, on the other 

 hand, grow almost solely near 

 their tips (Fig. 114), their indi- 

 vidual cells passing very quickly 

 elongation in growth of a typ- through the grand period, on 



narks; xf whole to grow evenly. This 



