166 BRITISH DESMIDIACEyK. 



WALKS.- -Generally distributed ! 



SCOTLAND.- -General ! Zygospores at Brimmond, 

 Aberdeen (Rot/ fy Bissett). General in the Outer 

 Hebrides ! 



IEKLAND. Donegal ! Majo ! Galway ! Kerry ! 

 Dublin and Wicklow (Archer). Armagh! Down! 

 Londonderry ! 



Geogr. Distribution.- -France. Germany. Belgium. 

 Austria and Galicia. Poland. Italy. Norway. 



e/ / 



Sweden. Bornliolm. Finland. N". Russia. Spitz- 



bergen. Nova Zembla. Siberia. Central China. 



India. Ceylon. Australia. Japan. Azores. United 

 States. Brazil. 



C. Portianum is generally distributed in the western boggy 

 areas of the British Islands, and it also occurs somewhat 

 sparingly in other districts. It is characterized by its elliptic 

 semicells both in front and vertical view,, by its open sinus, 

 its slightly elongated isthmus, and by its granulation. It 

 should be carefully compared with C. orbiculatum Ralfs and 

 C. istlimium West. 



The species was originally described by Archer from 

 Ireland, but that author did not give the details of the dis- 

 position of the granules. We have examined large numbers 

 of British specimens, more especially Irish ones, and we find 

 that the general arrangement of the granules is in vertical 

 series, about ten of which are visible in the front view of the 

 empty semicell. Very often the granules are also disposed in 

 indistinct oblique series, and in rare cases the disposition is 

 more or less irregular. Schmidle's " var. orihostichum" must 

 therefore be considered as in no way different from typical 

 Irish examples such as those originally examined by Archer. 



Messrs. Roy and Bissett found the zygospores in Aberdeen- 

 shire, and stated that they agreed with the figure given by 

 De Bary ( f Conj. ; 1858, t. 6, f. 50) of a zygospore which 

 that author erroneously referred to C. orbiculatum Ralfs. 

 De Bary's figure must therefore be taken to represent the 

 zygospore of (7. Portianum (vide PL 103, fig. 4). Confirma- 

 tion of this view is found in the fact that the zygospores of 

 the closely allied species C. orbiculatum and C. isthmium are 

 similarly furnished with elongated conical warts (consult 

 PI. LXXVII, figs. 8 and 9, and also fig. 17). 



The spiny zygospore figured by Wolle as that of C. 



