1916] Evans, — Notes on New England Hepaticae, — XIII 79 



3. Pobella pinnata L. Sp. Plant. HOG. 1753. Jungermannia 

 PoreUaDicks. Trans. Linn. Soc. 3: 239. pl.WJ.l. 1797. Junger- 

 mannia distans Schwein. Spec. Fl. Am. Sept. Crypt. 9. 1821. Mado- 

 theca Porella Nees (in part), Naturg. der enrop. Leherm. 3: 201. 

 1838. Madotheca involuta Hampe; Lehmann & Lindenberg, Pug. 

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

 Pot. 3 : 301 . 1805. Madotheca SuUivantii Ausl . Hull. Torrey ( Hub 3 : 

 lo. 1872. Porella SuUimntii Underw.; A. Gray, Alan., ed. (i, 709. 

 1890. Madotheca microrhyncha Tayl.; Stephani, Species Hepat. 4: 

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



The geographical distribution of P. pinnata extends, in North Amer- 

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

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

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

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

 Portugal. In North 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. There are certain 

 details, however, which the descriptions do not bring out very clearly, 

 and a few words about these may be in place. Attention will likewise 

 be called to certain synonyms of the species. 



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

 leaves, underlcaves 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 periehaetial bracts and 

 bracteoles a few slime papillae (or their vestiges) 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 

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

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

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



