143 



Cellulse longse 20 28 32 40//, latse 1620^, in sectione 

 alt ee 2024^. 



Perithalli cellules infimse omnes fere seque altas ac cellula? 

 hypothalli ; in, sectione transversali altiores quam Iata3, in sectione 

 longitudinali fere quadratic*, cellula? superiores gradatim de- 

 crescentes. 



Celluke altae 2428^, latae 20^. 



Nemathecia in thallo parvas maculas obscuras irregulares ef- 

 ficiunt, carposporis tripartitis zonatis et paraphysibus obtusatis 

 quorum cellulse 1V 2 altiores sunt quam latae. 



Nemathecia alta 200 ^. CarposporaB 100 //. Nemathecia cum 

 tetrasporangiis, cruciatim divisis. Tetrasporaa altaa 60 80 /^. 



Peyssonnelia simulans has received its name because it has 

 so many points in common with P. conchicola that I felt doubtful, 

 whether it might not be a form of P. conchicola but it can not 

 be identified with this alga and therefore I prefer to describe it 

 as a new species. 



P. simulans distinguishes itself from P. conchicola by adhering 

 loosely to the substratum; the collection of Dr. BORGESEN con- 

 tains entire loosened specimens, whereas P. conchicola adheres 

 firmly to the substratum. The colour is different in both algaa, 

 P. simulans being of a bright pink colour not red - and P. 

 conchicola of a red colour that fades partially away in drying. 

 The faded parts have a yellowish pink colour. 



It is true that as a rule colour is a bad characteristic of 

 algee but in the Peyssonnelia it is such a marked feature, that 

 it probably can be of great help in knowing the different species. 



P. simulans resembles P. conchicola by its hypothallus con- 

 sisting of straight-running filaments ending in a short, high apical 

 cell, which is higher than the filaments are at a little distance 

 from the top. Its perithallus is characterized by an almost square 

 lower cell, that divides at its top, seen in longitudinal section, 

 in two rows of cells (Fig. 140). This is often the case in species 

 of Peyssonnelia but seldom so regularly and in such a marked 

 way as in this species. Under slight pressure on the cover slip, 

 the cellrows loosen in vertical direction after decalcification and 

 this I have never observed in sections of P. conchicola. I could 

 study this alga thoroughly thanks to the kindness of Dr. A. FORTI, 

 who send me an authentic specimen of Dr. PICCONE for compari- 

 son. I may well thank him here for his kindness. 



The thallus of P. simulans is incrustated with carbonate of 

 lime; it is thin, the thickest thallus in Dr. BORGESEN'S collection 



