410 



Systematic remarks and descriptions extracted 

 from the preceding. 



40. Phonnidium autumn ale (Ag.) Gomont emend. 



Oscillatoria autumnaMs Agardh. 



Dispositio Algarum Sueciae, p. 36, 1812, e specim. Agardhi 

 in herb. Hofman-Bang. 



Phormidium autumnale Gomont. 



Monographie des Oscillariées , fragment II, p. 187, 1892, e 

 specim. authent. in herb. Hafn. 



Phormidium uncinatum Gomont. 



Essai de classification des Nostocacées homocystées, Journ. de 

 bot., IV, p. 355, 1890; Monographie des Oscillariées, fragment II, 

 p. 184, e specim. authent. in herb. Hafn. 



Thallo expanso tenue firmo vel saepius laxo , affixo vel 

 libère natante, atro-aerugineo, -virente, -chalybeo vel nigro, nitido. 

 Vagin is mucosis, distinctis vel in mucum chlorozincico jodurato 

 haud caerulescentem diffluentibus. Trichomatibus aerugineis 

 vel fuscescentibus , 3,5 ^ ad 9 a crassis , rectis vel subrectis, 

 parallelis vel varie intricatis , apicibus breviter attenuatis eximie 

 capitatis, rectis, curvatis vel leviter spiralibus. Articulis sub- 

 qvadratis vel diametro usqve ad 3-plo brevioribus; dissepimentis 

 saepe indistinctis freqventer granulatis; cellulis apicalibus calyptram 

 rotundatam vel depresso-conicam praebentibus. 



Gomont in his Monographie des Oscillariées distinguishes 

 the two species which were established by Agardh sen. in the beginning 

 of this century viz. Oscillatoria autumnalis and 0. uncinata as Phormi- 

 dium autumnale (formerly Ph. antliarium) and Ph. uncinatum. As 

 distinguishing characters between P. uncinatum and P. autumnale he 

 indicates the more robust trichomatas of the first one, the easily per- 

 ceptible uncinated apex and the fact, that this plant grows chiefly in 

 quick -flowing waters, while the second one, P. autumnale is more 

 slender and with less uncinated or even quite straight apex. This one is 

 generally an earth-alga and less frequently submers. At the same time 

 he says (1. c, p. 186) that the morphological distinction between the 

 two species may be uncertain when intermediate forms are present. 



