1920] Setchell-Gardner : Chlorophyc&ae 247 



are of rapid development and early maturity, so that their effective 

 season of growth may be short, and on the basis of their being, for the 

 most part, essentially tropical or subtropical species. Such warm 

 water species of rapid development may extend into zones of colder 

 surface waters by growing in the upper littoral belt where they may 

 take advantage of the temperatures of the air, or by inhabiting 

 shallow pools or lagoons the temperature of which is raised by the 

 influence of the atmosphere and sunlight. 



Key to the Species 



1. Cells separated, often widely from one another, seldom parenchymatous, un- 



branched 1- E. groenlandica (p. 248) 



1 . Cells usually distinctly parenchymatous, simple or more usually branched 2 



2. Cells not arranged in longitudinal rows except, at times, in very youngest 



parts 3 



2. Cells arranged in longitudinal rows in the greater portion of the frond.... 7 



3. Frond with more or less plentiful branches 4 



3. Frond simple or with few proliferations 5 



3. Frond beset with mostly simple, stout, spinelike branchlets 



6. E. acanthophora (p. 2,54) 



4. Frond flattened, branching from the margins 



2a. E. micrococca forma subsalsa (p. 249) 



4. Frond tubular compressed, branches contracted at the base, becoming 



broader above 4. E. compressa (p. 251) 



5. Cells 10-16m diam., fronds usually inflated and constricted, often of large size 



5. E. intestinalis (p. 252) 



5. Cells 4-8m diam., fronds usually short 6 



6. Membrane 8-10m thick, cells 5-7^ diam 3. E. minima (p. 250) 



6. Membrane 15-20^ thick, cells 4-5m diam 2. E. micrococca (p. 249) 



7. Frond simple, inflated and flexuous 8. E. flexuosa (p. 255) 



7. Frond simple or with occasional proliferations, not inflated 8 



7. Frond regularly branched. 10 



8. Frond narrowly linear, strongly compressed 10. E. marginata (p. 257) 



8. Frond filiform, capillary or tubular 9 



9. Frond capillary of few longitudinal rows of cells 12. E. torta (p. 258) 



9. Frond coarse, plainly tubular, of numerous longitudinal rows of cells 



9. E. tubulosa (p. 256) 



10. Frond beset with numerous thorn-like branches 



11. E. salina var. polyclados (p. 257) 



10. Frond proliferous, branches similar to main axes... 7. E. prolifera (p. 254) 



10. Branches of successive orders, tapering from base to apex 11 



11. Chromatophores filling the cell 12 



11. Chromatophores not filling the cell 13 



12. Ultimate ramuli and branch tips of a single series of cells 



13. E. crinita (p. 258) 



12. Ultimate ramuU and branch tips of more than one series of cells 



14. E. erecta (p. 259) 



13. UltimateramuUandbranchtipsof a single series of cells .15. E. plumosa (p. 259) 



13. Ultimate ramuli and branch tips of more than one series of cells 



16. E. clathrata (p. 260) 



