THE AERIAL ALGÆ OF ICP:LAND 



409 



sumed that he referred specimens of P. parmi v. minuta within the limits 

 in which I understand this form to this species. 



I have most frequenlly found tilis form on damp rocks covered 

 With moss and on purely mineral ground samples 25, 61, 68. 69, 129, 

 137, 253), but also in the vicinity of houses where il must be prcsumed 

 that some manure was present. 



Pinnularia stauroptera Grun. v. interrupta Cl. Cl. Svn. II, p. 83. V. H. 

 Syn. PI. 6 lig. 6. 



N. Icel. 140. 



Found in a ditch among desiccated algæ. 



Pinnularia subcapitata Greg. Cl. Syn. II, p. 75. Van Ileurck Syn. 

 PI. VI, lig. 22 Fig. nostra 30 b. 



E. Icel. 4, L. 114, 123, L. 125 — N. Icel. 169, 173. L. 217, L. 218, 

 L. 256 — N. W. Icel. 269 - W. Icel. L. 307, L. 338. 



In several of the samples there occurred specimens which were 

 considerably smaller than the typical form (L. 22//, br. 4,4/0, thus in 

 samples 217 and 218, but apart from their size these small 

 specimens agree perfectly with the typical P. subcapitata. 



For Denmark I came to the result (1915, p. 293 and 

 297) that P. subcapitata probably thrives e([ually well in 

 fresh water and on land. The same seems to be the case 

 in Iceland where Østrup found it in 51 samples from 

 fresh water. while I found it in 12 localities on land. 

 These, however, were of rather diverse kind, partly moss 

 on the ground and rocks, partly naked earth, partly from 

 the neighbourhood of hot springs, partly placcs near human 

 habitations abounding in organic subslances. Hence it is 



difficult to form any idea as to what lil'c conditions it 

 would require in order to thrive well. Deflandre found 

 the species on damp rock in Normandy (1926). 



Fi-. .30. 

 Pinnularia 

 snl>capitata 

 Grej^. a. var. 

 sublanceo- 

 laln n. var. 

 b. f. iijpica. 

 (X 1200). 



— — var. sublanceolata n. var. 



L. 17— 22/<, br. 4,5//, str. 11-14 in 10//. Valve lan- 

 ceolate with slightly rostrate, occasionally cjuite slightly 

 capitate, apices, in all other particulars resembles the species. Fig. 30a. 



E. Icel. 69, L. 125 - N. Icel. 160, L. 218. 



In samples 125 and 218 this varicty was found in company with 

 the species. Found only on moss on rocks and on fairly pure mineral 

 ground. 



Pinnularia viridis Nitzsch var. commutata Grun. Cl. Syn. II. p. 91. 

 Van Heurck Syn. PI. 5, fig. 6. 



E. Icel. 8, 25, 40, 92, L. 99, 124, L. 125, L. 128 - N W. Icel 140, 

 169, L. 217, L. 218 - W. Icel. 298. 



