STUDY OF A BRYOPHYTE 265 



374. Reproduction by Spores. — If possible, procure a 

 thallus with uprigiit pedicels bearing enlargements at the 

 top like those represented in Figures 500 and 502. These 

 are receptacles containing spore cases corresponding to the 

 archegonia and antheridia of the fern prothallium. Notice 

 their difference in form, the one (Fig. 502) umbrella shaped 

 and scalloped round the edges, the other (Fig. 500) rayed, 

 like the spokes of a wheel. The first produce antheridia 

 only, and the second archegonia. Examine both surfaces 

 of each, and then vertical sections, under a lens. Notice 

 that the antheridia grow from the upper surface of the 

 scalloped disks, the archegonia from the underside of the 

 rayed ones, concealed in the heavy covercles that depend 

 from the rays (Fig. 501). The archegonia and antheridia, 

 as in the ferns, produce different kinds of reproductive 

 cells called gametes, and so the thallus that forms the plant 

 body of the liverwort is the gametophyte and corresponds 

 to the prothallium of the fern. When one of the gametes 

 from an antheridium enters an archegonium and fuses 

 with the other kind of gamete contained there, an oospore 

 is formed as in the fern, which is capable of germinating 

 and producing a new growth. But instead of falling to 

 the ground and giving rise to an independent plant like the 

 sporophyte of the fern, the oospore germinates within the 

 receptacle and produces there an insignificant spore case 

 (/, Fig. Soi)> containing ordinary spores and thus repre- 

 senting in a reduced form the sporophyte that is so conspic- 

 uous a feature of the ferns. These spores, on germinating, 

 produce the liverwort thallus body or gametophyte, thus 

 completing the cycle of generations. Notice that in the 

 liverwort (and all bryophytes), the thallus or gametophyte, 

 is the important part of the plant and performs all the 

 vegetative functions, while the sporophyte is a small, insig- 

 nificant body that never becomes detached from the game- 

 tophyte and has no independent existence. In the fern 

 and other pteridophytes just the reverse is true ; the sporo- 

 phyte constitutes the beautiful plant body that we all admire 

 so much, while the gametophyte, though it does attain a 



