416 



BRYOPHYTES (MOSS PLANTS) 



Thus as compared with the Marchantiales, the Jungermaniales 

 have gametophytes more differentiated in form but less in struc- 

 ture, and have sporophytes characterized by a greater sterilization 

 of sporogenous tissue. 



Anthoceros. — Anthoceros is a representative of the Antho- 

 cerotales which is a very small group of inconspicuous Liverworts. 

 Anthoceros and its allied forms are the most interesting of all 

 Liverworts, because their structure suggests the steps by which 

 Pteridophytes, the Fern group, could have originated from the 

 Bryophytes. Anthoceros grows spread out like some of the 



Riccias and is common on moist 

 soil in north temperate regions 

 {Fig. 371). The gametophyte is 

 a simple thallus, much simpler 

 than that of the Marchantias. 

 The sex organs develop in sunken 

 areas on the top surface of the 

 thallus. 



The remarkable feature is the 

 sporophyte, which differs in a 

 number of ways from the spo- 

 rophytes of other Liverworts. 

 In the first place the sporo- 

 phyte is green, which means that 

 it is supplied with chloroplasts 

 and is thereby able to make 

 food for itself, although it has to depend upon the gameto- 

 phyte for water and mineral salts. This feature suggests the 

 independent sporophjrte of the Pteridophytes. The epidermis 

 of the sporophyte even contains stomata for allowing the air 

 to reach the green tissues beneath as in the leaves of higher 

 plants. Evidently, if this sporophyte had roots, it could live 

 independently of the gametophyte. In the second place there 

 is a core or central axis of sterile tissue called columella extend- 

 ing lengthwise through the sporophyte, and bands of spore- 

 forming tissue alternate with bands of sterile tissue around this 

 columella. The columella is a characteristic featiu^e of Moss 

 sporophjrtes, and in this way the Anthocerotales relate the 

 Liverworts to Mosses. If one imagines the bands of sterile 

 tissue which alternate with the bands of spore-forming tissue 



Fig. 371. — Anthoceros, showing 

 a gametophyte {g) bearing sporo- 

 phytes (s). X about 2. 



