FRESHWATER ALGÆ FROM TUDDAL IN TELEMARK. 161 



47. Roya obtusa (Breb.) W. & G. S. West. var. montana. 

 W. & G. S. West. 



Not uncommon, and sometimes in quantity. Size: long. 93 i-i, 

 lat. 6,5 !.i. Fig. 7, PI. V. 



Genus Cylindrocystis. Menegli. 1838. 



48. Cylindrocystis Brebissonii. Menegh. 



Very common. Pure gatherings could often be obtained. 

 1 find this species to be very variable in size, the smallest 

 specimens examined by me being only 42,5 u long, and the 

 largest up to 83 ^ti, the commonest size being about 50 ^t^ The 

 breadth was much less variable, generally about 20 ^, but up 

 to 25 a maximum. 



49. Cylindrocystis crassa. De Bary. 



Rare. I have only observed this species in one or two 

 samples. Size: long. 37,5 f.i, lat. 21,5 ^t. 



Genus Netrium. Näg. 1849. em. Liitkem. 1902. 



50. Netrium Digitus. (Ehrbg.) Ifzigs. & Rothe. 



Very frequent. In the most of the samples. Size : very 

 variable. Two specimens measured: long. 255 f.i, lat. 72 jli, 

 & long. 132 .«, lat. 38 ^t. 



51. ^ Netrium Naegelii. (Breb.) W. & G S. West. 



Very rare. Size: long. 105 f^i, lat. 21^. Somewhat smaller 

 than the typical form. 



52. Netriutn oblongum. (De Bary) Liitkem. 

 Fairly general. Size: long. 90 — 110 in. 



52 a. forma elongatum. 



Cells about IV2 times longer than the typical form, and also 

 more slender. Size: long. 185 /<, lat. 30 /n. 



52 b. var. cylindrwum. W. & G. S. West. 



Genera], but somewhat scarce. Size: long. 56,5 (tt & 80 ,u, 

 lat. 16 ^i & 20 ^. 



Nyt Mag. f. Naturv. LVII. 1919. 11 



