LIVERWORTS 



169 



the back of the thallus (Fig. 163). These bodies are round 

 and flat (biscuit-shaped) and many-celled, and falling out 

 of the cup they start new thallus bodies. 



Although the thallus body produces no spores, it does 

 produce sex-organs. In Marchantia, long, erect, stem-like 

 branches arise from the thallus, bearing at their summits 

 conspicuous disks that contain the sex-organs. The disks 

 containing antheridia are lobed or scalloped (Fig. 163); 

 while those containing the egg-producing organs are star- 

 shaped (Fig. 165). The two kinds 

 of disks are not found on the 

 same plant. 



93. The antheridium. The 

 sperm-producing organ is called 

 an antheridium, but it is very 

 different from the antheridia of 

 the Thallophytes. Instead of be- 

 ing a single cell, it is a stalked, 

 club-shaped or globular, many- 

 celled structure (Fig. 164). A 

 single layer of cells forms the 

 covering, and within it there is 

 a closely packed mass of small 

 cells, each one of which pro- 

 duces a sperm. The sperm is 



a very small cell with two long cilia, and these small 

 biciliate sperms are one of the distinguishing features of the 

 liverworts and their allies. 



94. The archegonium. The egg-producing organ is 

 called the archegonium, and it is very different from the 

 oogonium of the Thallophytes. Instead of being a single 

 cell, it is a many-celled structure, shaped like a flask with 

 a long neck, and within the bulbous base the single egg is 

 formed (Fig. 165, B, and Fig. 166). To this neck the 

 swimming sperms are attracted; they enter and pass down 



FIG. 164. Marchantia: antheridi- 

 um and two sperms. After 

 SACHS. 



