FRAMEWORK OF THE PLANT 



275 



addition to these elements, most proteins contain a small amount 

 of sulphur and some proteins also contain a small amount of 

 phosphorus. By chemically combining in certain proportions 

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

 sulphur, and phosphorus obtained from the soil, proteins are 

 formed, but as to how the proteins are transformed into living 

 protoplasm no one knows. 



Framework of the Plant. — Protoplasm, since it is a semi- 

 fluid, has no definite shape except when enclosed in a framework. 

 It is by means of a frame- 

 work that higher plants are 

 able to so shape themselves 

 as to be adjusted to the soil, 

 air, and sunlight. 



The cell walls constitute 

 the framework. They are 

 so joined as to divide the 

 plant into the compart- 

 ments in which the pro- 

 toplasts or individual 

 masses of protoplasm re- 

 side. The fact is, how- 

 ever, that each cell is en- 

 closed by walls of its own ; 

 but the adjacent walls of 

 neighboring cells are usu- 

 ally so closely joined that 

 the cells appear to be sep- 

 arated by a single wall. 

 Through very small pores in the cell walls, the protoplasts are 

 commonly connected by small protoplasmic strands, which afford 

 a means of communication between the protoplasts of neighbor- 

 ing cells. {Fig. 248.) 



The primary substance of which cell walls are formed is 

 cellulose, a substance closely related to sugar as its formula 

 (C6Hio05)n indicates. In the formula (C6Hi()()5)n each combina- 

 tion CeHioOb, of which an unknown (n) nmnber are combined in 

 forming cellulose, is a molecule of sugar minus a molecule of water 

 as may be seen from the equation C6H12O6 — H2O = CeHioOs. 

 Thus the formation of cellulose involves no other elements than 



Fig. 248.— Cells with protoplasm shrunken, 

 so that the fine strands of protoplasm extend- 

 ing through the cell walls and connecting 

 neighboring protoplasts may be seen. Highly 

 magnified. 



