100 Rhodora [May 



out. Some of the teeth, moreover, are large and compound and show 

 a development of secondary teeth. Teeth of this character arc repre- 

 sented in Fig. 1 1, which shows one of the sinuses between the lips of 

 the perianth, and also in Fig. 14, which unfortunately is taken from a 

 specimen without mature capsules. Sometimes a few surface cells 

 close to the mouth project slightly, as shown in Fig. 13. 



The sporophytic characters of P. platyphylla are well described by 

 Miiller. It might perhaps be added that the two spirals in the 

 elaters are continuous at the extreme ends and form loops. This 

 interesting feature is brought out by Schiffner and is very evident in 

 both European and North American material. The writer is inclined 

 to follow Schiffner and Miiller in restricting the name /'. platyphylla 

 to plants in which the elaters are bispiral. The difficulties in deter- 

 mining material without capsules will be discussed under P. jtlafy- 

 pkylloidea. 



The third species of Porella which has been reported from New 

 England is P. rivularis (Nees) Trevis., the full description of which 

 by Howe ' may be consulted. This species has been more or less con- 

 fused with both P. pinnata and P. platyphylla. Although the name 

 P. rivularis has been in widespread use for a considerable period, 

 Miiller- has recently shown that the oldest synonym for the species 

 is J ungermannia Cordaeana Hiiben. 3 and therefore describes it under 

 the old name Madotheca Cordaeana (Htiben.) Dumort.' In order 

 to avoid t he publication of a new combination, Dumortier's name 

 will be employed in the present paper. J\I. Cordaeana is especially 

 at home on stones and rocks along mountain brooks. In such locali- 

 ties it is more or less subject to inundation, but in dry seasons may be 

 exposed to the air for considerable periods. In very shady places it 

 sometimes grows on trees close to the base. Miiller comments on the 

 variability of the species, due to environmental conditions, and notes 

 its occurrence in North America, northern Africa, and western Asia, 

 as well as in Europe. In the writer's opinion, however, the records 

 not only from New England but from other parts of eastern North 

 America are based on incorrect determinations, as will be shown below. 



In general appearance M. Cordaeana resembles /\ pinnaia very 



' Hull. Torrey Club 24: 519. 1897. 



■ Hahenhorsl's Kryptogamen-Florn 6'-': 585. 1915. 



s Hepat. Germ. 291. 1831. 



' Hecueil d'obs. sur lea Jung. 11. 1835. 



