414 .loiis. noYi: piieiiskn 



Rhopalodia ventricosa Kiitz. O. M. Meislcr 1912, p. 201. Tal". 35. lig. 8. 

 E. Iccl. 7. L 2."). 28, 78, 85. L. 92 — N. Iccl. L. 135, 140. 184. 



Tilis vciv \vi(lcs|)rc;ui species occurrcd in a fairly ^reat niimbcr of 

 spcciiuens iii a (luantity of samples, and was Ibiind witli cell contents 

 in samples from ratlier drv localilics 92. 135). 11 is tliiis cerlain Ihat 

 il mav occiir as an aerial species. th()u<<h it is evideiiliy niiKli commoner 

 in fresli water. (O s trup 190 sam|)Ics). 



X. Nitzschieæ. 



Ilantzschid Grun. 



Hantzschia amphioxys (Khrb.^ Grun. 



Il has long been known that certain forms of this species are of 

 common occurrence on llie groiind. lluis by Pfi t zcr 1882 p. 405\ Var. 

 xerophila, in particular. is recorded by Grunow from sucb localities, 

 but in reality forms thai must be referred to var. (lenuina Grun. are no 

 less common on thc grt)und as I have previously staled Boye V. 1915 

 p. 294 . It has been observed by Deflandre on damp rocks 1926). 

 In cultures of soil from various depths Moore and Karrer (1919, p. 296) 

 found the species ver}' common down to a depth of 100 cm. According to 

 renewed invesligations by .Moore and Nellie Carter 1926 Ihtiilzschia 

 did not prove very common in the samples of soil examined. It was 

 found. however, in two samples from a dcjjlh of down lo 2 feet 6 inches. 

 B. .Muriel Bristol instituted a series of cultures of soil-samplcs (1920, 

 p. 42 which had been dried for a shorter or longer period. In nearly 

 all of them she found small forms of H. ami)hioxijs which must pre- 

 sumably be referred to the two above-mentioned varicties of Grunow. 

 Thc samples had been dried for 4 — 26 weeks, so thcsc experimenls show 

 that the species has a very considerable power of withstanding desicca- 

 tion. I found 1915 p. 275 that H. amphioxijs was alive and able lo 

 move in a preparation in water of a sample of soil only containing 

 5,2 j). c. of water. 



— — var xerophila Grun. Grun. Diat. Fr. Jos. Ld. 188 1. p. 47. 



E. kel. L. 14, L.15, L. 40, L. (18, L. 77, L. 78, L. 92, L. 121 - X. Icel. 

 135, L. 137. 138.160, L.162, L.173, L. 182. L.185, L. 196. L. 217, L. 218, 

 L. 219, L. 241, 252a. L. 253. L. 254 — \V. Icel. L. 298, L. 307, L. 309a, 

 L. 321. L. 327 - S. Iccl. 1.. 282, 295. L. 352, 353, 372, L. 381. 387, 395 — 

 Vcstmannaeyjar L. 407. L. 408, L. 409. 



.\ccording to Grunow (1. c. var. xeropiiila has the same appearance 

 as var. (/enuina which is stated to be furnished mit stumpfen. etwas 

 vorgezogenen Knden". In most of the Icelandic specimcns of \i\r. xcro- 

 /)hil<i the apices were plainly capitate and oftcn somewhal upward curvcd. 

 there were. iiowever. some specimcns whosc a|)ices were simply produced. 

 In a single sample 68) there were some specimcns wilh two pronounced 

 gibbositics on llie venlrai side near thc apices. and in other sam|)les, 

 too, something similar was found. but in less marked degree. 



