CARBOHYDRATES, CHITIN AND CUTIN 



287 



primary cell wall. It also rules out the possibility of direct interference 

 by auxin with the cellulose frame. 



The increased plasticity of elongating tissues (Heyn, 193 1 ; Soding, 

 193 1 ; ZoLLiKOFER, 1955) is probably due to the bipolar protrusions 

 of the cells, and the effect of different ions on the cell elongation (Wuhr- 

 MANN, 1937) must be sought in the influence on the cellulose-synthe- 

 sizing cytoplasm. 



TABLE XXV 



CHEMICAL COMPOSITION OF MAIZE COLEOPTILES IN mg/COLEOPTILE 



(blank AND FREY-WYSSLING, I941; WIRTH, I946) 



Forces of growth. The classical cytologists considered the turgor 

 pressure to be the driving force of cell elongation in plants. The cell 

 expansion was ascribed to water absorption only. This is not the case, 

 however, as seen from Table XXV, where the chemical composition 

 of expanding maize coleoptiles is summarized. Since there are no cell 

 divisions when the coleoptiles elongate from 9 to 55 mm, each cell 

 must increase all its constituents, in the same proportion as indicated 

 by Table XXV. The increment of cell substances appears to be very 

 considerable (Blank and Frey-Wyssling, 1941, 1944), being almost 

 proportional to the cell elongation. If the figures relating to the 5 5 mm 

 coleoptile are divided by 6, the values for a coleoptile section of 9 mm 

 length are obtained (Table XXV, last column), which compare 



