THE MARCHANTIA GROUP 



285 



lower surface of the receptacle (Fig. 252, A) between the fringes. 

 The sporophyte is more complex than hi the Riccia types. The 

 lower part (Figs. 252, B\ 253, A) becomes a small organ of at- 

 tachment to the gametophyte, called the foot, through which 

 it obtains water with food in solution. The upper part becomes a 

 spore case, developing numerous spores, and among them spirally 

 marked filaments, termed elaters (Fig. 

 253, ), which are stiff and elastic and 

 help to distribute the spores. The elaters 

 are developed from cells in the young 

 spore case. The spore case is carried 

 beyond the fringe of the receptacle (Fig. 

 252, B) by the elongation of the region 

 above the foot, which forms a stalk. The 

 presence of a foot and stalk in addition 

 to the spore case marks a decided ad- 

 vance over the simple sporophytes of the 

 Riccia types, which consist of the spore 

 case alone. 



It is very important to note that the 

 sporophyte has this close attachment to 

 the gametophyte and is dependent upon 

 it for water and food in solution, because 

 it shows that the sporophyte of the liver- 

 worts really lives in large part like a 

 parasite upon the gametophyte as a host. 



289. The Jungermannia group. This 

 assemblage (order Jungermanniales] is 

 very much the largest group of the liverworts and contains 

 more than three thousand species. They are known as the leafy 

 liverworts because most of them have long stems, with delicate, 

 moss-like leaves. The leafy liverworts are frequently mistaken 

 for mosses, since they are common on tree trunks and in shaded 

 situations. But they have a creeping habit, and there are two 

 crowded rows of large leaves (Fig. 254, A), one on each side of 



FIG. 253. The sporophyte 

 of Marchantia 



A, longitudinal section of 

 sporophyte showing spore 

 case and foot attached to 

 the hase of the archego- 

 nium: e, a special envel- 

 ope. B, an elater 



