PLANTS 329 



highest class of plants. Their composition is quite 

 complex, and they perform the functions necessary to 

 their life, growth, and reproduction in complicated ways. 

 There are other plants which do not have flowers and 

 in which the function of reproduction is accomplished in 

 other ways than by the production of seeds. Some of 

 these plants are composed of but a single cell, which per- 

 forms all the functions of the plant. Reproduction in 

 such plants takes place when the cell separates into two 

 cells, thus forming two plants. Higher forms of flowerless 

 plants are reproduced by spores which contain a very 

 small portion of protoplasm capable of reproducing its 

 kind of plant. For convenience in study, the flowerless 

 plants may be divided into algae, fungi, mosses, and 

 ferns. 



Algae. The algae are the lowest form of plant life, 

 but they resemble higher plants in some respects ; they 

 all contain chlorophyll and are able to manufacture 

 starch from water and carbon dioxide. Algae vary in 

 size from simple one-celled plants to the giant kelp of 

 the Pacific Ocean, which frequently attains a length of 

 several hundred feet. A common alga is the simple one- 

 celled variety that is frequently found on the bark of 

 trees and on rocks. It has a greenish color and may be 

 found in almost any forest. 



Pond scum is another alga known as spirogyra. It can 

 be found floating on the surface of almost any stagnant 

 pond. The cells of the spirogyra are placed end to end, 

 so that they form long threads. It is heavier than water, 

 but enough bubbles of oxygen cling to the masses of 

 threads to cause them to float. The oxygen is given off 

 by the plants as starch is formed, as in higher plants. 

 The spirogyra grows by a division of cells and also pro- 



