MORPHOLOGY 21 



ally entirely neglected and overlooked owing to its 

 minute size. The mosses also have an alternation of 

 generations, but in their case the reverse is true, and 

 what we know as the moss plant is the prothallial 

 generation, which has elaborated itself so that it has 

 much the appearance of a leafy plant, though it is so 

 different in its origin from the leafy plants of other 

 groups. 



In the algae we find the plant body represented by 

 simpler structures. The whole algal body is often 

 called a thallus, and this has regions which correspond 

 more or less closely to root, stem, and leaves in the 

 more elaborate and larger of the seaweeds. In most 

 algae, however, there is little differentiation among 

 the cells, and in the simple hair-like forms so common 

 in the fresh water ponds and streams, there are only 

 green vegetative cells and reproductive cells with no 

 modification into true " organs." 



In the fungi we get also a very simple plant body, 

 generally like that of the thread-like algae. Sometimes 

 many of these filamentous cells intertwine to form 

 quite large and apparently complex bodies, the toad- 

 stools for instance, but the plants have not truly differ- 

 entiated organs. 



It is interesting to notice how a number of the higher 

 plants have degenerated and lost the differentiation 

 of their parts. For example, the Dodder (Cuscuta), 

 which grows with such deadly success on the Clover 

 and Furze, appears to have lost all differentiation of 

 stem, root, and leaves, and has become a mere tangle 

 of fine pinkish fibres, which attach themselves to the 

 stems of other plants and draw all nourishment from 

 them. Its flowering, however, it must do for itself, 

 and the parts of its flowers, which appear in relatively 



