410 University of Calif arnia Piiblications in Botany [Vol. 8 



19. Fronds caespitose 10. E. simulans (p. 422) 



20. Fronds 1 cm. or more high 21 



20. Fronds less than 1 cm. high 26 



21. Fronds twisted into dense rope-hke threads 20. E. breviarticulatus fp. 429) 



21. Fronds more or less loose and caespitose 22 



22. Ramuli mostly alternate 23 



22. Ramuli mostly secund 25 



23. Main filaments 25-40^ diam 24 



23. Main filaments 40-60^ diam 19. E. oviger (p. 428) 



24. Gametangia broadly fusiform 17. E. Parksii (p. 427) 



24. Gametangia ellipsoidal, obtuse 18. E. Mitchellae (p. 428) 



24. Gametangia broadty ovoid, mucronate 7. E. mucronatus fp. 419) 



25. Gametangia 60-lOOyu long 16. E. granulosus (p. 426) 



25. Gametangia 40-60m long 22. E. granulosoides (p. 431) 



26. Fronds penetrating the host 27 



26. Fronds not penetrating the host 30 



27. Cells of the main filaments less than 30^1 diam 28 



27. Cells of the main filaments more than 30^ diam 29 



28. Gametangia fusiform, scattered on the upper parts of the fronds 



30. E. socialis (p. 437) 



28. Gametangia ovoid to ellipsoid, mostly near the base of the fronds 



31. E. flocculiformis (p. 438) 



29. Gametangia cylindrical, many opposite E. cylindricus f. codiophilus (p. 433) 



29. Gametangia globular, mostly alternate 32. E. globifer (p. 438) 



29. Gametangia fusiform, mostly alternate 34. E. Bryantii (p. 440) 



30. Fronds less than 1 mm. high 23. E. affinis (p. 432) 



30. Fronds more than 1 mm. high 31 



31. Gametangia chiefly cylindrical 32 



31. Gametangia not cylindrical 33 



32. Fronds 1-2 mm. high 24. E. cylindricus (p. 432) 



32. Fronds 7-10 mm. high E. cylindricus f. acmaeophilus (p. 433) 



33. Fronds in dense hemispherical tufts 34 



33. Fronds more or less caespitose 35 



34. Fronds much branched, 2-4 mm. high 25. E. hemisphericus (p. 434) 



34. Fronds mostly simple, 1-2 mm. high.E. hemisphericus f. minor (p. 434) 



35. Cells over 20^ diam 26. E. Saundersii (p. 434) 



35. Cells less than 20m diam 36 



36. Gametangia long-acuminate, up to 400/xlong.27. E. acumdnatus (p. 435) 



36. Gametangia not long-acuminate, up to 250/x long 37 



37. Fronds 9-12/x diam 28. E. ellipticus (p. 436) 



37. Fronds 14-15^ diam 29. E. chitonicola (p. 436) 



1. Ectocarpus siliculosus (Dillw.) Lyngb. 



Frondfs tufted, feathery, loose, more or less entangled below, 

 yellowish or brownish, pseudodichotomously branched below, alter- 

 nately secund above ; branches erect or, at times, somewhat recurved, 

 never patent, not fascicled ; sporangia ovoid to ellipsoidal, 30-65^ 

 (usually 50ju,) long, 20-27/x broad, sessile and erect or diverging on 

 a 1-3-celled pedicel ; gametangia usually long subulate-conical, seldom 



