CHAPTER XIX 

 THALLOPHYTES 



WE HAVE now come to the lowest great division of the plant 

 kingdom,, the Tliallopliytes, which are subdivided into three 

 divisions, the Algce, the Fungi and the Bacteria. The second 

 and third of these groups do not contain chlorophyll and are 

 therefore quite different in habit from all other groups of the 

 plant kingdom. 



The algae vary greatly in both size, structure and color, but 

 all of them contain chlorophyll and are able to do the work of 

 photosynthesis or starch-making. The range from the small, 

 one-celled plant which cannot be seen without the aid of the 

 microscope, through delicate thread-like forms up to the enor- 

 mous sea-weeds, possessing root-like, stem-like and leaf-like 

 organs. They are widely distributed throughout the world and 

 are of much greater importance than we might at first suppose. 

 Minute forms are found in great numbers, causing the green 

 stain on the bark of trees and stones and brick walls, in the 

 streams and pools, and in the seas, gulfs and bays and even the 

 broad ocean itself. 



The types are entirely too numerous to mention in a work 

 of this kind, and therefore, we must content ourselves with a 

 study of two or three of the most common forms. Many of the 

 unicellular forms found in moist places on trees and walls repro- 

 duce by simple division, each division resulting in the forma- 

 tion of two new plants, each similar to the parent. Each plant 

 is capable of performing all the function of a much larger and 

 more complex plant; i.e., the absorption of water and minerals 

 in solution and of nitrogen, the taking in of carbon dioxide, and 

 photosynthesis and reproduction. 



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