302 PLANTS 



with a microscope, it is found to consist of small cells 

 (Fig. 246). Often several cells adhere to one another. 

 The cell consists of a wall and of living substance within, 

 called protoplasm (pronounce this, pro'-to-plasm). The 

 denser part of the protoplasm is called 

 the nucleus of the cell. In the proto- 

 plasm are the grains of chlorophyll that 

 give the groups of cells their green ap- 

 pearance. 



If the protococcus cells are examined 

 carefully, some will probably be seen 

 FIG. 246. Protococcus, that have dividing lines across them. 



greatly magnified. 



Each of the two halves may be divided 

 further, and the new cells thus produced may separate 

 from one another. As a result we have a whole group 

 of cells. Each cell contains its own protoplasm, nucleus, 

 and chlorophyll, and is an independent plant. This 

 formation of new cells is a method of reproduction. 

 It is called reproduction by cell-division. 



Another alga is called spirogyra. This is a "scum" found in 

 ponds; its cells are attached end to end, so that they produce filaments, 

 or threads. The chlorophyll bodies are arranged in spirals. 



Spirogyra carries out reproduction in a different way from proto- 

 coccus. Two cells in neighboring filaments bend their cell walls toward 

 each other, until they touch. Then the two walls between them dis- 

 appear, and the contents of one cell pass over into the other cell. The 

 materials of the two cells form a body called a spore. The spore, like 

 the embryo, endures through the winter, and then germinates, produc- 

 ing a new plant. The spirogyra is thus reproduced by a sexual method. 



324. Fungi. Fungi (singular, fungus) form a large 

 group of plants that have no chlorophyll, and cannot, 



