202 



THE PLANT WORLD 



nearly equal size fuse to form a single cell is called conjugation 

 The result of this process of fusion is a thick-walled resting cell 

 which is called a zygospore (zl'go-spor). This cell thus formed can 

 withstand considerable extremes of heat, cold, and dryness. 

 After the zygospore is formed, the cell walls break and the zygo- 

 spore falls to the bottom of the pond. Under favorable conditions, 

 it will germinate and form a new filament. 



Self-Testing Exercise 



The simplest green plants are the (1). The (2) of 



two cells of nearly equal size to form one cell is called (3) . This 



method of reproduction is characteristic of (4). A 



(5) is a thick-walled resting cell. 



PROBLEM Vm. WHAT IS THE LIFE HISTORY OF A MOSS 



PLANT? 



The Bryophyta consist of two groups of plants, the liverworts 

 and the mosses. Both are small plants and nearly all forms live 



on land. They show 

 a much greater de- 

 velopment of tissues 

 than the algae and 

 may be either thallus- 

 like (liverworts) or 

 have stems with 

 rootlike projections 

 (rhizoids) and very 

 simple leaves, as 

 the mosses. 



The Moss Plant. 

 One of the mosses 

 frequently seen and 

 easily recognized is 

 the " pigeon- wheat " 

 moss. A leafy moss 

 plant has rhizoids, 



The life history of a moss. Refer to the numbers in your . , 



text and work out the stages in the life history. an Upright Stem, and 



