The Genus Riccardia in Chile. 177 



R. mycophora from the other Chilean species of Riccardia. In 

 separating it from R. Negcri, the more flaccid texture of the plant 

 should be taken into consideration also, together with the more 

 irregular branching. In R. Negcri, moreover, the large interior 

 cells in the marginal portion of the thallus show conspicuously 

 through the small-celled surface layer, but nothing comparable 

 with these is present in R. mycophora. 



20. Riccardia nudimitra (Steph.) comb. nov. 

 Ancura nudimitra Steph. Sp. Hepat. 6: 35. 1917. 



Specimens examined: Sholl Bay, Clarence Island, Harlot 62 

 (B., type of Ancura nudimitra') ; Halt Bay, 1868, Cunningham 

 162 (M.) ; near Mt. Richardson, Staten Island, 1882, Spegazsini 

 75 (M.). No other localities have been reported. 



Although a differentiation of the thallus into stolons, prostrate 

 caudex, and ascending photosynthetic branch-systems is clearly 

 indicated in R. nudimitra, these various kinds of axes are connected 

 with one another by intermediate structures. The irregularity 

 thus produced is supplemented by a marked irregularity in the 

 branching. The latter feature perhaps indicates a certain relation- 

 ship to such species as R. tcnax, but the more immediate allies of 

 R. nudimitra seem to be found in R. alcicornis and R. fuscobrun- 

 nea. The plants are pale brown or greenish brown, becoming 

 almost black in the older parts, and grow in intricate depressed 

 mats, sometimes mixed with other bryophytes. Rhizoids are 

 scantily produced and seem to be largely if not wholly confined to 

 the stolons. 



The main axis (Fig. ii. A, B) is at first prostrate, although it 

 usually turns an edge rather than a surface to the substratum. 

 Sometimes the prostrate position is retained for a long period, but 

 the apical portion usually curves upward after a while, gives 

 rise to a photosynthetic system and has its growth brought to an 

 end. The axis is firm and distinctly flattened, measuring usually 

 1-1.5 cm. in length, 0.4-0.7 mm. in width and 0.2-0.25 mm. in 

 thickness. On the sides it thins out gradually to edges which vary 

 from rounded to subacute. Sometimes there is no sign whatever 

 of a wing ; sometimes a narrow band along the edge is paler than 

 the median portion and gives the appearance of a wing, but even 



