370 M or pho genetic Factors 



into the composition of the wall but produces its effects through changes 

 in the cytoplasm ( Sorokin and Sommer, 1929 ) . 



More conspicuous effects of calcium have sometimes been observed. 

 Pearsall and Hanby (1925), for example, found that in Potamogeton 





10 r 



en 



g 8 



o 



X 



i 



^ A 



O * 



Z 



UJ 



o 

 o 



2 - 



/+>- D.G.S.B. 



.00 



.01 



.05 

 ppm BORON 



.10 



.50 



§4 r 



8 



UJ 



^3 



<£ 2h 



>- 

 x 



■O.6.S.B. 





X.J^— <l 



UTAH 10-B 



-L 



.00 



x 



Q. 



.01 .05 



ppm BORON 



.10 



.50 



Fig. 17-3: Relation of boron to cell-wall thickness in three varieties of celery. (From 

 A. R. Spurr. ) 



excess calcium made the leaves broader and their cells more numer- 

 ous. 



In field plots abundantly fertilized with potassium, plants of flax, 

 ramie, oats, and willow showed marked increase in number and size of 

 bast fibers (Tobler, 1929). Hemp was but slightly affected. 



