METABOLISM IN LIVING PLANTS. 



467 



Of the various sorts of building materials, the albumens must first be con- 

 sidered; they are to be reckoned as the most important constituents of living 

 protoplasm. Although their chemical composition has not as yet been ascertained 

 with complete certainty, it is known that, besides the carbohydrate constituents, 

 albumens contain nitrogen and 0'8-17 per cent of sulphur; that carbon with 



Fig. 123. Crystals and Crystalloids. 



leaf of the Virginian Creeper (Ampelopsis hederacea). In some of the cells are clustered- 

 n one cell there is a single envelope-shaped crystal 



Phalli caninus. 



eedle from a bundle of raphides. ecion o a P" 



^^ 



magnified. 



many perhaps with more than a hundred, atoms takes part in the construction 

 of a molecule, and that consequently the molecules of albumen are very 1 

 In order that a carbohydrate may become transformed into an albuminous 

 nitrogen and sulphur, at any rate, must be drawn into the combination. 



