THE CELL WALLS OF PLANTS 83 



The conflicting evidences and interpretations involved in the con- 

 troversy centering about the ellipsoidal bodies cannot be reviewed hei-e, 

 but the subject is one that cytologists will continue to follow with th(> 

 greatest interest. The theory of the origin of cellulose in j^lastids is 

 especially intriguing in view of the fact that starch, which resembles 

 cellulose so closely in chemical composition, is elaborated in such cell 

 organs. A completely satisfying answer to the question of whether these 

 two materials, which are about the onl}^ solid substances deposited in 

 large amounts by plant protoplasts, have similar or dissimilar cytological 

 origins would indeed be a major and welcome achievement. 



