36 



THE CELL AND PROTOPLASM 



tied cellulose, and for various optical, physi- 

 cal, and chemical properties of cell walls 

 in general. It should be recognized, how- 

 ever, that according to such a modification 



(Fig. 7) resembles so closely the finer 

 visible structure of swollen secondary walls 

 that a question arises whether there are two 

 distinct sizes of fibrils, or rather a series of 



Fig. 10. Swollen transverse section of a cotton hair jjrown during the i)eriod of teiniieratiiri' lliu-tua- 



tions shown in Fig. 9. Total enlargement, X 5130. After Kerr. 

 Fig. 11. Transverse section of the ringless secondary wall of a cotton hair, grown under constant ilhi- 



mination and temperature. Total enlargement, approximately x 5250. After Anderson and Kerr. 

 Fig. 12. Transverse section of the secondary wall of a cotton hair, showing experimentally induced 

 lamellae. Total enlargement, appidximately x 5250. Photographed from one of Ken's jnoparations. 



of NJigeli's hypothesis, the ci-ystallite or tliese structures wiiicli grade down in size 



micelle loses its individuality. fi-om macrofibrils to microfibrils and to 



Frey-Wyssling's modified conception of micelles 60 A or less in diametei-. Altlioip^li 



the submicroscopic structure of cellulose reliable factual data for coiicinsiveiy an- 



