J32 



JOHS. BOYE PETKHSKN 



conlenls ol" ;r ci'll ;il(tii}4 a suiucwhal obliqiie phuie 

 of division. Humuc hy division inlo 4 or <S i-cUs by 

 rcpcaled bipaiiilion. Wiu'liu'r tbc rcproduclive cells 

 tims fornuMl devclop into zoospores or a|)lanospores 

 I liavo nol bccn able to ascertain irom tbe driod 

 niatcrial at band. Tbc dan^btcr ccIIs arc libcraled 

 by Ibe wall ol' tbc niotbcr ccll bcin«^ dissolvod at 

 onc end. Tbcy bavc a somewiiat dill'ercnt sbapc 

 from tbf rulI-j»ro\vn cclls. l)t'in;4 nioic obb)n<^ or 

 lu si tor ni. 



Tberc was sonic dill'crcncc bctwct-n tbc two 

 sani|)lcs. In sample No. 349 Fig. 35 tbc cells were 

 on tbc wbolo Iar<»cr Iban in sam|)Ic No. 326 (Fi{». 36), 

 and tbc sporanj^ia most f"rc<|ucntly contaiiicd 8 spores 

 in contrasl to sample 32(i wberc tbey rarcly con- 

 taincd more tlian 4. Howcver, I regard tbese diller- 



ences betwecn tbc two sam|)lcs as a mere variation most pr(»bably due 



to dilTcrent lifc-conditions. 



Fif?. -My. 

 Chlorelht r//;/osfi n.sp 

 From sam|)le 326. 

 1,X 1200). 



Ulothricales. 



Ulot b r icaccæ. 



Ulothrix zonata Kiitz. Cbodat 1902, p. 267. 

 H. Icel. 55 c. 



(2an probably only grow in wafer or in |)laces wbere tberc is plenty 

 of water. It was lound at tbe cnlrance ol' a small ri^cky cavc wilb 

 dripping water in company witb Trihonema bombijcinum and numerous 

 Diatoms especially Meridian circiilare). Tbc tilamcnts attained a dia- 

 meter of 22 — 35 II. 



Hormidium flaccidum Kulz.) A. Br. A. P.raun Hab. Algen No. 2480 

 (cited alter (lay 1891. p. 79. 



Ulotbrix liaccida Kiitzing 1849. j), 349. 



F-:. Icel. 55b. 88. 91 — N. Icel. 179, 217 - N. W. hel 2(58. 269 — 

 S. Icel. 294, 352. 387. 



This species is nolcd for its unusually great power of adaptation 

 in regard to dill'erent substrata iHansgirg 1887. p. 83. W i 1 1 e 1912. 

 |). 449, l'nymaly 1924. p. 223). 



In Iceland 1 bave found il on irrorated rocks, partly frccly exposed 

 to tbe ligbt, parlly in a small cavc wbere it bad formed numerous 

 resting aplanospores witb spiny ouler wall as describcd by \Vi 1 1 c (191 2, 

 p. 452, Tall. 14, lig. 20) from a growtb in a similar locality in Norway. 

 It was not possible for me. bowever. to see tbe aplanospores lying witbin 

 tlic cells of tbc motber plant. Tberc was plenty of water present in tbe 

 localities mentioned. I bave. bowever, also found it in drior- localities, 

 on moss-covered slones, on cartb. on lurf in Ibe wall ol a bousc. on 

 wall s. 



