PRINCIPAL GROUPS OF PLANTS. 



83 



divisions and bears the archegonia (Fig. 46) on the lower sur- 

 face, known as the archegoniophore ; these being borne on separate 

 plants. In Riccia, the simplest of the Liverworts, the sporangium 

 is enclosed by the thallus and the spores are not liberated until the 

 decay of the plant. 



(2) The JuNGERMANiA Group, known as "Leafy Liver- 

 worts " or " scale mosses," includes those forms which are more 



Fig. 48. Anthoceros gracilis, one of the liverworts. A, thallus with 4 sporogonia; 

 B, a ripe elongated sporogonium, dehiscing longitudinally and showing two valves between 

 which is the slender columella; C, D, E, F, various forms of elaters; G, spores. — After 

 Schilfner. 



or less moss-like and develop stems and small leaves. The sporo- 

 gonium has a long stalk and the capsule is 4-valved, i.e., separates 

 into four longitudinal sections at maturity. 



(3) In the Anthoceros Group (Fig. 48) the gametophyte 

 is thallus-like and very simple in structure, the sexual organs being 

 embedded in the thallus. The sporogonium is characterized by a 

 bulbous foot and an elongated, 2-valved capsule. Like the thallus, 



