CHAPTER XXIV. 



LIVERWORTS (HEPATIC^). 

 (Marchantia polymorpha.) 



230. Form of marchantia. The marchantia (M. polymorpha) 

 has been chosen for stud) 7 because it is such a common and 

 easily obtained plant, and also for the reason that with com- 

 parative ease all stages of development can be obtained. It 

 illustrates also very well certain features of the structure of the 

 liverworts. 



The plants are of two kinds, male and female. The two 

 different organs, then, are developed on different plants. In 

 appearance, however, before the beginning of the structures 

 which bear the sexual organs they are practically the same. 



The plant forms a flattened, green, leaf-like body which lies 

 on the damp soil or clings closely to wet rock. It is shaped 

 somewhat like an irregular ribbon, the margins more or less 

 wavy, and the plant is branched in a forked manner as shown 

 in fig. 1 1 8. Upon the under side are numerous hair-like 

 bodies, the ' ' rhizoids, ' ' which serve the purpose of root hairs 

 in absorbing food solutions, and they also attach the plant to 

 the substratum. The growing point of the thallus is in the 

 little depression at the free end. 



For fuller studies of the liverworts and for the sexual organs 

 see the author's larger " Elementary Botany/ 7 Chapters XXII 

 and XXIII. 



Exercise 47. 



231. Male plants. Examine both surfaces of the "thallus" as the leaf- 

 like body of the liverwort is called. Note where the rhizoids are attached. 

 Sketch the plant, showing the rhizoids, the form of the thallus, and the um- 



139 



