292 COLLEGE BOTANY 



and produce new gametophytes. Tke complete life history is 

 illustrated in Fig. 141. 



The genus Biccia also belongs to the Marchantiales and con- 

 tains a number of species, some of which are terrestrial and 

 others aquatic. They are smaller than M. polymorpha and the 

 antheridia and archegonia remain embedded in cavities of the 

 thallus. They are the simplest of the Hepaticoe. 



The Jungermanniales contains a larger number of species 

 than either of the other two groups. They grow under conditions 

 ranging from the extremely wet to the extremely dry. They are 



most abundant in the tropics and 

 gTow most commonly on the ground, 

 on tree trunks and on leaves. They 

 are divided into two groups, the thal- 

 lose forms, which resemble the Mar- 

 chantiales, and the foUose forms, 

 which resemble the mosses, but there 

 is a gradual gradation between the 

 two groups. However, the distinc- 

 tive characters of the J ungermanni- 



Marchantia polymorpiia bearing two aleS IS tO be fouud in the archeTOnia 

 archegoma] branches; (o) also a ^ 



single antheridial branch from a and the SPOrO'phyte. 

 male plant. , ^ 7 



The Anthocerotales is a small, 

 temperate zone group, which is thought by many workers to 

 represent the ancestral forms of the Pteridophytes. We cannot 

 discuss this order in a limited work of this kind. 



It will be noted that in the Ilepatioa? the gametophyte is 

 much larger than the sporophyte and that there are no true roots, 

 stems or leaves. There is a differentiation of the cell structure 

 but no collenchyma, sclerenchyma, fibrous, tracheary, sieve or 

 laticiferous tissues. < 



The Musci or mosses are also a very old group of plants which 

 are more highly differentiated than the Hepaticw. They ai-e 

 widely distributed and were much more abundant during the 

 carboniferous age of the earth's history than at the present time. 



140. — (a) female plant 



