164 Howe : Riccia Beyrichiana and Riccia dictyospora 



1 



development of the inner and outer faces becomes especially ap- 

 parent when these faces are compared in profile. The spines or 

 papillae of the outer face are then seen to be considerably longer, 

 projecting 6-9 11, while those of the inner faces project only 4 or 5 p, 

 Riccia Beyrichiana, with which, on account of its dark purple 

 er surface and the geographical association, Riccia dictyospora 

 is perhaps most likely to be confused, is a considerably smaller 

 plant* with thick rounded-obtuse, or, at the thallus-apex, merely 

 acute, margins, which occasionally bear short cilia. In R. dictyos- 

 pora, on the other hand, the thallus-margins are thin and submem- 

 branous and no cilia have been seen. But more striking distinctive 

 characters are to be found in the spores. In Riccia Beyrichiana 

 the mature spores are so extremely opaque that very little 

 can be made of their surface-markings until they have been well 



■ 



saturated with glycerine after having been soaked out in water. It 

 is nevertheless seen at once that they are distinctly angular, though 

 often flattened or irregular in form, and that they are very large, 



40/* in maximum diameter. In glycerine it can 

 be determined that the inner faces are almost absolutely smooth, 

 being roughened only by very fine granulations or sometimes by a 

 faint suggestion of areolae. The outer face bears areolae which 



6- 



are 1 5-20 fi in diameter 



~pora. The 



boundaries of these areolae are less elevated than in many species 

 of Riccia and the outer face as a rule appears rather obscurely pap- 

 illate, yet in profile view it sometimes exhibits papillae 4 or 5 ft in 

 length. The seams or wings at the angles of the spore are often 

 narrow and obscure, but they sometimes broaden here and there 

 into expansions 6-8 /x in width. It is possible that the opacity of 

 the spores of Beyrich's plant has slightly increased during the many 

 years of preservation, but age can be in no way responsible for the 



* None of the specimens that we have seen from the Lindenberg herbarium is more 



mm 



it is probable that after nearly seventy years of drying they do not quite regain their 

 former dimensions. In regard to length, however, it is to be noted that Lehmann and 

 Lindenberg in the original diagnosis ( Lehm. Pugill. 7 : 1. 1838) describe the « fronds " 

 as "2-4 lineares," while Stephani (/. c.) has recently described them as "usque 10 

 mm." The antheridia of Riccia Beyrichiana we have not seen, paucity of material 

 standing in the way of extended search, so we are unable either to confirm or deny 

 Stephani' s statement that the species is monoicous. 



