152 The Living Plant 



main parts of one continuous mass. As to the function of the wall, 

 that is perfectly obvious, — it is the skeleton of the cell, the me- 

 chanical support for the gelatinous cytoplasm, which has not 

 enough firmness of texture to raise itself unaided an inch from the 

 ground. It is interesting to let the imagination picture what 

 would happen to the loftiest and stateliest tree, if, by some subtle 

 chemical magic the cell- walls could be suddenly re-converted back 

 to the gases from which they were made; the protoplasm would 

 simply collapse to the ground as a shower of slime. 



The reader at this point will observe how different in principle 

 is the construction of the skeleton in plants as compared with 

 animals. In animals, in conformity with the much higher de- 

 gree of division of labor in their parts, certain cells are set aside 

 to build the skeleton for the entire individual, either a deeply- 

 buried bony skeleton as in man, or a surface skeleton of lime 

 or horn as in crabs and insects; while all of the remainder of their 

 cells are without hard walls and devoted to other functions. 

 In plants, however, every individual cell has a wall around it- 

 self, and the collective mass of these walls makes up the skeleton 

 of the plant. Such a mass of cell-walls, however, by no means 

 represents, though one might naturally think so, a lot of origi- 

 nally separate walls fused together. Observation of growing parts 

 always shows (figure 101) that the new walls formed between 

 dividing cells are thrown across the protoplasm as single solid 

 structures, which may or may not in time become split and 

 divided between the two cells. Thus the cell- wall system of a 

 plant is one single mass from the beginning, just as is the wall 

 mass of a building; and the protoplasm lives in cavities therein, 

 precisely as people live in the rooms of a house they have built. 

 The reason for the difference in the method of skeleton building 

 by animals and plants is plain enough upon reflection. The 

 method of animals permits jointing and muscular movement, 

 as it must in order to allow the most fundamental of all animal 

 activities, — locomotion in search of food; the method of plants 



