How Plants Grow 



37 



are the new parts formed? Where in a plant is 

 growth most actively going on? To answer these ques- 



FIG. 20. Diagrammatic representation of a group of plant cells. Above is 

 a cell with the wall cut and a part of it lifted to show the contents. Below are 

 cells cut crosswise and lengthwise. All plants and animals are built up of these 

 cell units ; but, of course, many kinds of cells are very different from the box- 

 like structures here shown. 



tions it is necessary to explain the structure of a plant. 

 The cells of a plant. If a thin section or piece of a 

 plant is examined under a microscope, it is seen to be 

 made of tiny units that are called cells. Each cell, like 

 a loaf of bread, has length, breadth, and thickness. The 

 outer part of the cell is a wall, and if the cell is living, 

 within the wall is a soft, living material that appears 

 somewhat like white of egg. In a full-grown plant cell 

 the most active part of its substance is found chiefly 

 in a layer just within and completely lining the wall, 

 in strands of this material that extend from the lining 

 layer to a rounded body called the nucleus, and in the 



