1920] Setchell-Gardncr: Chlorophyceae 245 



Entcromarpha is a gemis of the Ulvales characterized by its tubular 

 frond which is usually narrow, although much dilated at times in 

 the case of certain varieties of Entcromorpha intcstinalis. The species 

 are usually branched, although some are normally simple or, at times, 

 proliferous. This definition or characterization leads us to exclude 

 E. percnrsa and its allies, E. aureola and its allies, and E. Linza, the 

 two former being referred each to its own genus, viz., Percursaria and 

 Capsosiphon respectively, and the last to the genus Ulva. The par- 

 ticular reasons for thus excluding from the genus EntermiorpJm 

 plants heretofore commonly referred to it will be given under the 

 respective genera or species, while the general reason is that Entcro- 

 morpha thus reduced is more readily defined and apparently more 

 natural. In addition to these changes, we have added to the genus 

 Enteraniorpha tlie species commonly known as Moivostroma groen- 

 landicum, because in detail of habit, at least, it is very much closer 

 to EnteromorpJia than to Monostroma and not so very diverse from 

 some species of Entcromorpha even in structure. 



The more characteristic species of Enteroniorphu have the cells 

 arranged closely set, and parenchj-matous in appearance, but certain 

 species show, at times, the cells separated considerably from one 

 another by an intercellular jelly and this condition is normal in 

 E. groenlandica, which, for tliis reason, usually has been placed under 

 the genus Monostroma. The cells are arranged in longitudinal rows 

 in many species. Some species show a continuance of this arrange- 

 ment even on into the adult condition, while others soon lose it. The 

 chromatophore generally fills the cell as seen in surface view, but in 

 a few species it occupies only a small portion of the surface of the cell. 



Much is to be determined in Entcromorpha, as is also the case in 

 Monostroma and TJlva, from the thickness, shape and proportions of 

 the cells, and the disposition of the enclosing intercellular substance 

 in cross sections of the membrane. Such sections also show the degree 

 of compression of the frond and whether the walls are completely 

 separated from one another or not. 



In branching there is great variation, not only in the genus, but 

 witiiin many of the species. It has seemed best, nevertheless, to 

 consider the method of branching as one of the chief characters in 

 separating the species. 



The species of Entcromorpha present difficulties whieli liave not 

 yet been entirely overcome. The habit is of importance, but varies 

 considerably either under environmental changes or with age in such 



