140 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 



regard to its anatomical structure, but it difTers from this alga by its 

 hypothallic filaments, running in little flabelliform groups over the 

 substratum; the colour of both algæ is also different, P. Boergesenli 

 being of a dark purple colour with a greenish hue over it, P. Harvey- 

 ana of a bright red colour. Lastly P. Boergesenii is also character- 

 ized by the distinct veins running from the centre towards the 

 periphery. 



Found in shallow water, St. Croix, White Bay. (N. 1537 n, 1546 n, 

 168511). Rust of Twist (N. 1442). In alcohol and dry specimens. 



4. Peyssonnelia (Cruoriella) Nordstedtii nov. spec. 



Thallus tota superficie inferiore adhærens, paulum calcarius, 

 colore ignota, diametro usque ad 4 centimetrum, constans hypo- 

 thallo et perithallo. Hypothallus constat filis repentibus, juxtap- 

 positis, parva flabella efficientibus. Cellula apicalis fdorum alta 

 et brevis, in sectione longitudinali altior filis hypothalli. 



Cellulæ longæ 28—36—40^, latæ 16—20—28,« et ± 28// altæ. 



Perithallus constat filis adscendentibus, stratum satis crassum, 

 denique fissum formantibus. Pars inferior hujus strati peril, pars 

 superior hypothallum novum efficit, cum radiculus uni- et pluri- 

 cellularibus partem inferiorem tegente, radiculis iis in partem in- 

 feriorem penetrantibus. 



Cellulæ altæ ± 12—20—36 u, latæ 12—16—20/^. Nemathecia 

 cum tetrasporis quadripartitis, cruciatis, tantum immatura visa. 



Peyssonnelia (Cruoriella) Nordstedtii^) resembles an alga col- 

 lected at the island of Nias, Sumatra, that I have called in my 

 manuscript of the Siboga-algæ, later on to be published, P. Nord- 

 stedtii. Both algæ have in common a frond of soft texture, only 

 slightly incrustated with carbonate of lime and the peculiar way 

 of renovating the frond. 



P. Nordstedtii belongs to the subgenus Cruoriella on account of 

 its hypothallus consisting of filaments branching by repeated dicho- 

 tomy, which branches grow until other filaments, crossing their way, 

 stop their growth. The branching filaments form little elongated 

 fan-shaped groups, springing from a principal axis with larger 

 cells than the cells in the fan-shaped groups, just like what we 

 have seen in P. Boergesenii (Fig. 143). 



Characteristic of P. Nordstedtii is the way in which the peri- 



1) Named in honour of and in gratitude to Prof. O. Nordstedt at Lund, 

 the learned algologist, to whom I owe so many graceful acts of kind- 



ness. 



