38 



THE CELL AND PROTOPLASM 



13 



Fl(i. 13. I)ia<ir;nii illustrating clia iiyos in i\\e orientation of cellulose in a o-lavered si'condarv wall. 

 Fig. 14. Transverse seetioii of wall pliotograjjlied in jiolarized liijlit lietween crossed Xicols (■ Kitd). 

 Fig. ].1. J)iagrani illustrating a M layered secondary wall. Tlic stipjiled layer is n(ui cellulosic and 



truly isotro|>ic. 

 Fig. 1(). Transverse seclion of wall [iliotogra])lied in iiolarizcd light lietweeii crossed Xicols (\1'J80). 



