1920] Setchell-Gardner : Phycological Contributions 281 



Enteromorpha groenlandica has always been puzzling as to its 

 proper placing. While technically it may seem to belong to the genus 

 Monostroma, under which it was originally described, more properly 

 than to any other genus of the Ulvaceae, yet its slender filiform habit 

 certainly more closely resembles that of some species of Enteromorpha. 

 From Enteromorpha, however, it differs in not having its cells set 

 sufficiently closely together to be parenchymatous in appearance. It 

 is at first solid, becoming hollow only late, but never rupturing longi- 

 tudinally and opening out into a membrane as do the characteristic 

 species of Monostroma. Certain species of Enteromorpha show a 

 tendency towards abundance of intercellular jelly at times, while 

 certain species of Monostroma are parenchymatous. It seems best to 

 us, therefore, to transfer this species to Enteromorpha. 



Monostroma areolatum sp. nov. 



Plate 30 and plate 31, figure 2 



Thallo delicatissimo, lubrico, 20-35 cm. alto, sessili, juveno saccato, 

 mox fisso et lobos late ovatos aut obovatos, undulatos, plicatos et 

 crispatos formanti, dilute viridi ; membrana distincte minuteque areo- 

 lata, 9-12/A crassa; cellulis rotunde angulatis, 6-7/a crassis in sectione 

 transversali subsphericis, in areolis quibusque aggregatis. 



Frond very delicate, lubricous, 20-35 cm. high, sessile, saccate when 

 young, soon splitting and forming numerous, long, broadly ovate, or 

 obovate, undulate, plicate and crisped lobes, pale green ; membrane 

 distinctly and finely areolate, 9-12/^ thick; cells with rounded angles, 

 6-7/x diam., subspherical in cross-section, grouped within each areole. 



Growing on Zostera in quiet waters. Sitka, Alaska. Type no. 

 3924, Gardner. 



This species of Monostroma is exceedingly beautiful and is among 

 the most delicate and flaccid of the genus. The frond remains saccate 

 for only a brief period, attaining a height of only a millimeter or two. 

 The sack then breaks and the membrane spreads out at once, early 

 developing small lobes. Finally a few primary lobes are established 

 and these develop numerous secondary lobes. The gro\\'th on the 

 whole margin greatly exceeds that of the interior, and this results in 

 the production of a great number of folds, making the margin very 

 much crisped. In the thickness of the frond and shape of the cells 

 M. areolatum closelj^ approximates M. zostericola Tilden. The cells 

 of the latter are, however, more angular and more closely placed and 

 the frond is not divided into areolae. There is a marked difference 



