1916] Evans, — Notes on Xew England Hepaticae. — - XIII 79 



3. PoRELLA pixxATA L. Sp. Plant. HOG. 1753. J ungermannia 

 Porc/Za Dicks. Trans. Linn. Soc. 3: 239. pl.20,f.l. 1797. Junger- 

 viannia distans Schwein. Spec. Fl. Am. Sept. Crypt. 9. 1S21. Mado- 

 theca Porella Xees (in part), Xaturg. tier europ. Lebenn. 3: 201. 

 183S. Madotheca involiita Hampe; Lehmann & Lindenherg, Pug. 

 Plant. 7: 10. 1838. Cairndishia Porella Carruth. Seemann's Jour. 

 Bot. 3: 301. 1865. Madotheca Sulllrantii Aust. Bull. Torrey Club 3: 

 15. 1872. Porella Sullivautii Underw.; A. Gray, Man., ed. 6, 709. 

 1890. Madotheca nu'crorhi/ncha Tayl.; Stephani, Species Hepat. 4: 

 251. 1910. [Text figs. 1-13.] 



The geographical distribution of P. piniiata extends, in Xorth Amer- 

 ica, from Xova Scotia westward to Ontario and Minnesota and south- 

 ward to Cuba, Florida, and Louisiana, numerous stations being known 

 from Xew England. In Europe its range is restricted to the British 

 Isles and the western coast of France, with a possible extension into 

 Portugal. In Xorth America the species is abundant; in Europe, 

 exceedingly rare. It grows on stones and logs in streams as well as 

 on the banks, and is completely submerged during a part of the year. 

 Apparently the sporophytes reach maturity only when the plants 

 are exposed to the air. 



The species has been repeatedly described so that little need be 

 said about its general features and great variability. Th^re are certain 

 details, howe\er, which the descriptions do not bring out \'ery clearly, 

 and a few words about these may i)e in place. Attentiou will likewise 

 be called to certain synonyms of the species. 



The complete, or almost complete, absence of marginal teeth on the 

 leaves, underleaves and bracts, in a genus where teeth are so frequently 

 present, is one of the most important characteristics of P. pinnata. 

 Close to the dorsal base of the lobe, to be sure, close to the inner base 

 of the lobule and along the margins of the perichaetial bracts and 

 bracteoles a few slime papillae (or their \estiges) can be demonstrated 

 (Fig. 12) and these are sometimes borne on short stalks, but even here 

 anything approaching an actual tooth in size is exceedingly rare. 



The lobes of the leaves (see Fig. 1 ) which are ovate to oblong in form 

 and rounded at the apex, are attached by an arched line and are com- 

 monly plane except close to the lobule, where the margin is slightly 

 inflexed. In plants exposed to the air this portion of the margin is 

 often more or less involute. At the dorsal base the lolie is somewhat 

 dilated but scarcelv enough to be called cordate; at the ventral base 



