CARBOHYDRATES 275 



One of the chief constructive processes of protoplasm is the 

 formation of more protoplasm. As plants and animals grow, 

 cells enlarge and multiply, and consequently the amount of 

 protoplasm must increase. More of the elements of chromatin, 

 nucleoli, cytoplasm, and all other protoplasmic substances must 

 be formed. 



As to the chemical composition of protoplasm in its living 

 state, we have no definite knowledge. We learn from the analyses 

 of dead protoplasm that it consists chiefly of proteins, and pro- 

 teins are considered its essential constituents. When plants are 

 analyzed chemically, their protoplasm is recorded as protein. 

 Proteins are composed chiefly of carbon, hydrogen, oxygen, and 

 nitrogen. In addition to these elements most proteins contain 

 a small amount of sulphur and some contain phosphorus. By 

 chemically combining in the proper proportions the carbon, 

 hydrogen, and oxygen of the sugar with the nitrogen, sulphur, 

 and phosphorus obtained from the soil, proteins are formed, but 

 the transformation of proteins into living protoplasm is not under- 

 stood. 



Carbohydrates. The carbohydrates consist chiefly of cellu- 

 lose, sugar, and starch. Here belongs the photosynthetic sugar. 

 The carbohydrates are so named because they contain hydrogen 

 and oxygen in the same proportion as they occur in water (H 2 O). 

 None of the carbohydrates are far removed chemically from the 

 photosynthetic sugar. No other elements than carbon, hydro- 

 gen, and oxygen are involved and the transformations are mostly 

 simple chemical processes. The carbohydrates are the most 

 abundant of plant products, constituting about three-fourths of 

 the dry weight of the kernels of cereals and from 25 to 50 percent 

 of the dry weight of straw, hay, and fodder. 



Out of cellulose plants construct their framework. Protoplasm 

 is a semi-fluid, maintaining no definite shape unless enclosed. In 

 multi-cellular plants a framework is necessary to enclose and pro- 

 tect the protoplasts and afford shape to the plant body. By 

 means of a framework the higher plants so shape themselves as 

 to be adjusted to the soil, air, and sunlight. 



Cellulose is built by the protoplasts into cell walls, and the cell 

 walls are so joined as to constitute the frame work. Each proto- 

 plast constructs about it walls which enclose a compartment in 

 which the protoplast lives and works. The adjoining walls of 



