THE AERIAL ALGÆ OF ICKLAND 417 



IMitzschia Hantzschiana Rabenli. Cl. und Grim. Arct. Diat. p. 99. 

 Van Heiirck Syn. PI. 69, Hg. 1. 



N. Icel. L. 217. 



Found among mosses on a stone in Stora Gjå« near Myvatn. Re- 

 corded by Hustedt 1922 p. 100) as growing on iiberrieselte Moosrasen«. 

 However, it is no doubt predominantly hydropbilous. 



Nitzschia fonticola Grun. Cleve und Grunovv Arct. Diat. p. 97. 

 Van Heurclv Syn. PI. 69, fig. 15— 19. 



E. Icel. 113. 



Possibly an accidental intermixlure in the sample. 



Nitzschia Kutzingiana Hilse. Cl. und Grun. Arct. Diat. p. 96. V. H. 

 Syn. PI. 69, lig. 24—26. 



E. Icel. 8 — N. Icel. L. 215, L. 217, L. 241 — \V. kel. 327 — S. Icel. 

 381, 386, L. 387 — Vestmannaeyjar 401. 



This species is characterised by a slightly silicified valve, lanceolate 

 with slightly protracted apices. The striæ are very difficult to couiit. 

 The dimensions are rather variable, and small forms olten occur on eartii. 

 The dimensions of the specimens fpund ranged wilhin tlie following 

 limits: L. 15—28 ii, br. 3,3—4,4//, str. very fine, carinal dots 14 — 18 in 10 //. 



I have found it in Denmark on various subsirata, but moslly on 

 garden and forest soil. Ostrup only found it in Iceland in one sample 

 from fresh water, hence it must be assumed to live a predominantly 

 terrestrial life in the island. though not in very dry sjjols. .My finds 

 allow of no conclusion in regard to its requirement of organic nourish- 

 ment. Moore and Karrer (1919 p. 296) found it in soil down to a 

 depth of 20 cm. 



Nitzschia Palea W. Sm. Cl. et Grun. Arct. Diat. p. 96. Van Heurck 

 Syn. PL 69, hg. 22 b. 



E. Icel. 113, 128. 



The specimens found showed the following dimensions; L. 25— 33 //, 

 br. 3,9— 4 /f, str. abt. 30, carinal dots 10—12 in 10//. Østrup found the 

 species in 83 samples from fresh water, so it can hardly in any marked 

 degree be capable of living on the ground in Iceland. I have arrived 

 at the same result for Denmark. Bristol mentions 1919, p. 98) having 

 found it alive in a culture of a sample of soil 50 years old; she like- 

 wise States (1920, p. 71) that she has found it in samples of soil. She 

 may, however, have confused it with the nearly related s|)ecies e. g. 

 N. Kiltzingiana. Moore and Carter state (1926, p. 118 that Ihey have 

 found it living in the earth at a depth of more Ihan 4 feet. 



— — var. perminuta Grun. Cl. et Grunow Aict. Diat. j). 97. 



E. Icel. 7, 28, 128 - N. Icel. 169, 252 - X.W. Icel. 264 - S. Icel. L.386. 



Differs from .V. Kiilziiujiana by the valve being more strongly silici- 

 fied and narrower, while the carinal dots are as a rule somewhat coarscr. 



