84 Rhodora [April 



previously referred to M. platyphyUa [i major, thus ascribing to the 

 two species ranges of ^•ariabiHt3^ different from those at first assigned. 

 As to which conclusion was correct he made no attempt to decide. 

 In spite of this uncertainty both species were recognized as valid in 

 the Synopsis Hepaticarum, published a few years later by Nees von 

 Esenbeck, in collaboration with Gottsche and Lindenberg. 



Lindberg, in his revision of the Scandinavian species of Porella, 

 published in 1869/ expressed the opinion that Nees von Esenbeck's 

 " M. j)latyi)hyUoidea" was a mixed species. He considered that part 

 of it belonged to the var. major of P. platyphyUa, and that the other 

 part (which he thought might be synonymous with the original 

 Jmigermannia platyphyUoidea) was a synonym of P. Thuja (Dicks.) 

 Lindb. A few years later - he added the interesting observation that 

 he had examined many North American specimens labeled P. platy- 

 phyUa but that they were all referable to P. Thujay and he commented 

 on the rarity and restricted range of this latter species in Europe. 

 Soon afterwards he published the combination Porella platyphylloides 

 (Schwein.) Lindb.'' and the same name reappears in his last general 

 synopsis of the Scandinavian bryophytes.* Apparently he used this 

 name as a substitute for P. Thuja, although this conclusion could 

 hardly be deduced with certainty from his published writings. If he 

 did make this substitution, it is difficult to understand why he pre- 

 ferred Schweinitz's specific name to the older name of Dickson, and 

 it is to be regretted that he did not explain his use of the name P. 

 platyphylloides more fully. In any case, however, it is clear that he 

 considered Schweinitz's species distinct from P. platyphyUa. 



Among American writers the tendency has been to define P. platy- 

 phyUa in a broad sense. This is the course pursued by Howe ^ in his 

 treatment of the North American species of Porella, published in 1897. 

 He admits that the species is very variable and that the common 

 form in America corresponds with the Jungermannia platyphyUoidea 

 of Schweinitz better than with the common European form. He 

 maintains, however, that the European form does occur in America 

 and that there are so many transitional conditions that any attempt 

 at segregation would be ill-ad\ised. 



A few years later an important paper on certain European species 



1 Acta Soc. Sci. Feun. 9: .329-345. 1869. 



J Ibid. 10: 493. 1875. 



3 Hepat. Utveckl. 20. 1877. 



« Muse. Scand. 3. 1879. 



'Bull. Torrey Club24: 521. 1897. 



