212 STRUCTURE AND LIFE HISTORIES 



ANTHOCEROS 



194. The Gametophyte. One of the most important 

 groups is the genus Anthoceros, including several different 

 kinds or species. The plant body, or thallus (Fig. 156), is 

 roughly circular or semicircular, with numerous rhizoids 

 growing from the ventral surface. It increases in size at 

 numerous growing points on the margin of the thallus, and 



FIG. 155. A leafy liverwort (Porella navicularis) . Female plant, about 

 natural size. (After M. A. Howe.) 



is green from the presence of chlorophyll in the cells. 

 There is only one chloroplast in a cell, in contrast to the 

 numerous chloroplasts in each cell of the mosses and ferns. 

 195. Reproductive Organs. The antheridia are found 

 just back of the growing points, near the middle of the 

 lobe. In some species they occur in groups (Figs. 157 

 and 1 59) , in other species singly (Fig. 1 58) . They develop. 



