UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



BOTANY 



Vol. 8, No. 2, pp. 139-374, plates 9-33 July 14, 1920 



THE MARINE ALGAE OF THE PACIFIC COAST 



OF NORTH AMERICA 



CHLOROPHYCEAE f^ /-.^^ V*^ 



L I K R A r* Y 1 



WILLIAM ALBERT SETCHELL 



AND 



NATHANIEL LYON GARDNER 



Subclass 2. CHLOROPHYCEAE kuetzing 



Thallophytes containing only the pigments, chlorophyll and xantho- 

 phyll; thallus varying from strictly single cells ( uninucleate \ or 

 more or less simple or complex colonies (as in the Protococcales), to 

 multicellular individuals which are either made up of cells (i.e., 

 uninucleate divisions, as in the Ulvales, Schizogoniales, and the 

 Ulotricales) or are coenocytes (i.e., of multinucleate divisions), the 

 latter being either septate (i.e., provided with partitions, as in the 

 Siphonoeladiales) or destitute of septa (as in the Siphonales), and 

 ranging in size from microscopic forms to individuals of more than a 

 meter in at least two dimensions; cell walls varying in structure and 

 composition, mostly of cellulose but sometimes largely of pectose, 

 occasionally more or less externally mucilaginous, generally simple, 

 moderately thick and structureless, but at times thick and variously 

 stratified, occasionally incrusted with lime ; nuclei well developed ; 

 chromatophores usually distinctly differentiated, of varjdng shape 

 and number, often containing starch centers, or pyrenoids, and 

 colored by chlorophyll and xanthophyll, the former usually in excess ; 

 reproduction vegetative, by non-sexual spores, and by zj^gotes ; vege- 

 tative reproduction by cell division, fragmentation, and by gemmae 



