268 JOHs. navK pktkhskn 



k-iur . Finally did Tilden 11)10 j). :U). :{2) readmil llie dillViencc in 

 size betwcen tht' cells as a principal dislinj^uishing character which 

 agrees with the two exsiccata, she cites, viz. Fhyc. Bor. Am. Nr. 251 and 

 1302. On llie other li;ind, she (h)es not mention nnylliin'^ alxmt 

 crystals. 



As \ve have scen, the varioiis authors do nol al all agree nol cven 

 with themselves II as lo the nianiu-i- in whicii Ihe two species ;or va- 

 rieties mav be separated. 



In order to investigate liic characters more closely 1 have cxamined 

 all the exsiccata ol" the two species whicii I liavc been able lo get hold 

 of, and the results ol" Ihis investigation is recordcd in the i)resenl tMble. 

 In the firsl column mcasurements ol" a numbcr ol" cells from cach sanii)l(' 

 are to be found. The numbers indicale the thickness of the cells. Iheir 

 length, on Ihe other band, I have not nicasured as it is very variable. 

 In the second column the external lorm of Ihe colony is described; ils 

 solidity could not be determined on Ihe basis of exsiccata. The third 

 column records the results regarding the determinations of the colour 

 of the colonies by means of Klinksieck el Valettc: Code des colours. 

 In the fouilli column is slated whether crystals (-[-) or not (-f-) are to 

 be found in the colony. In the liftb column Lemmcrmanns determi- 

 nations of the various samples are recorded, and in the sixth column 

 Tilden s. Finally in the seventh column the samples own designation 

 of the species. Almost all the exsiccata show about the same cell-dia- 

 meter except Phycothcca Bor.-Ani. Nr. 1302 which bas especially small 

 cells, and Hauck et Hicbter Phycothcca universalis nr. 193 which also 

 has rathcr small cells. In specimens from Iceland I found thai the size 

 of the cells iii tho individual thallus mav vary just as much as between 

 all of the examined exsiccata, viz. from 3,3—6,2 //. There is no noti- 

 ceable difference in the size of the cells between the two exsiccata which 

 A. Braun originally emjiloyed for Ihe establishment of the dilferences 

 between A. prasiiut and .4. stiujnina, viz. Bab. Alg. nr. 1572 and Kutz. 

 Dec. nr. 29. I therefore opine, like Bichter, thai this circumstance may 

 be disregarded as a distinguishing character. 



If we now consider the other characters, we will lind that in some 

 cases they unile in such a manner in Ihe individual specimen thai it 

 might be determined either to A. slaf/niiut or var. pnisiiut, e. g. according 

 to Lemmermann 1910. In other cases the characters are mingled, so 

 that Ihe individual bas one character which agrees with .\. slagnina 

 and another agreeing with A. pnisiiut. This fad seems in ilself to indi- 

 cale that we have in reality to do with only one systematic unit and 

 not two as generally supposed since the time of A. Braun. 



We will now consider the individual characters one by one. With 

 regard lo colour some variation is ap|)arenl in that some individuals 

 are brownisli, others more pure green, and olhers again having a bluisli 

 tint. The majority of Ihe s|)ecimens have a colour which almost corre- 

 sponds lo Codex nr. 326 or 330—33. A few are more brownish like 

 nr. 308 or :»04. whereas Wiltr. el Nordst. nr. 1596 a approaches nr. 352 

 whicii has a bluisli linl. The specimens collccled by me in Iceland 

 have exactly the same colour. 



