38 Gardening 
nucleus itself. Within the living cell there is much 
watery material known as the cell sap. 
Fic. 30. Part of a section cut lengthwise through the tip of an onion root, as 
seen through a microscope. The entire root tip is composed of cells which are 
shown in different stages of division in the lettered series. It is through the 
multiplication of the cells and the increase in size of the older ones that growth 
takes place. 
All the parts of a plant are composed of cells. The 
roots, stems, and leaves are each built up of a multi- 
