CHAPTER VIII 



LIVERWORTS 



90. Summary. As an introduction to liverworts it is 

 well to state the most important facts in reference to the 

 Algae and Fungi. The Algae and Fungi together consti- 

 tute the first great division of the plant kingdom, known 

 as Thallophytes. The name means "thallus plants," and 

 "thallus" means a body usually prostrate and having no 

 special vegetative organs as leaves and roots. Such a 

 definition cannot be very rigid, for some Algae cannot be 

 said to have strictly thallus bodies, and in the higher groups 

 thallus bodies also occur; but the name is a convenient one 

 to apply to all plants below the liverworts. 



As the study of the higher plants is begun, the important 

 progress made by the Thallophytes must be kept clearly in 

 mind, for the liverworts start with this progress behind 

 them. The important progress may be stated as follows: 



(1) Increasing complexity of the plant body. Beginning 

 with single isolated cells, the plant body reaches con- 

 siderable complexity among the Thallophytes, in the form 

 of simple or branching filaments, plates of cells, and masses 

 of cells. 



(2) Appearance of spores. Beginning with reproduction 

 by vegetative multiplication, the Thallophytes soon develop 

 special cells for reproduction (spores) , and produce them not 

 only in abundance but in a variety of methods and forms. 



(3) Appearance of sexual cells. After ordinary spores 

 appear, the Thallophytes also introduce a third form of 



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