70 L. HILLIS- COLIN VAUX 



This scheme could fit into either the Bold- Wynne or Round systems, 

 but is shown in Table IX as part of the Round scheme of classification. 

 The effect of my proposal is to unite the Codiales-Derbesiales group of 

 Feldmann (1954), which was also done by Rietema (1975), with the 

 name Derbesiales. The proposed scheme also recognizes the distinctive- 

 ness of the Caulerpa-Halimeda-Udotea series. 



Table IX. Modified Scheme of Orders for the Eusiphoniidae 



Class Bryopsidophyceae 



1 

 Subclass Eusiphoniidae 



1 1 ^ i 1 



Orders DERBESIALES CAULERPALES DICHOTOMO- PHYLLO- 



SIPHONALES SIPHONALES 



Caulerpaceae 



I 

 Caulerpa 



I 

 Udoteaceae" 



Halimeda, Penicillus, Rhipocephalus , 

 Tydemania, Udotea, Avrainvillea, 

 Boodleopsis, Callipsygma, Chlorodesmis, 

 Cladocephalus, Geppella, Pseudochlorodesmis, 

 Pseudocodium, Rhipidodesmis, 

 ( = Chlorodesmis, at least ^.^.), 

 Bhipilia, Rhipiliopsis 



"■ Many of the genera are tentatively placed herein and require cytological and life- 

 history studies. 



Within the Caulerpales, I have followed, for the present, the tradi- 

 tional separation into two families, Caulerpaceae (which is monogeneric) 

 and Udoteaceae, since we know very little about a number of genera in 

 the Udoteaceae. One of the characters used to separate these two groups 

 (Bold and Wynne, 1978), the presence of trabeculae or wall ingrowths 

 in the filaments of Caulerpa, has been observed in the walls of the 

 filaments of the segments of Halimeda tuna (Borowitzka and Larkum, 

 1977). 



I have not accepted within the Caulerpales, either as delimited 

 above or in the sense of Bold and Wynne (1978), the separation, by 

 Gepp and Gepp (1911), of Udotean genera into calcareous (Udoteae) 

 and non- calcareous (Flabellarieae and Codieae) categories, with C odium 

 and Pseudocodium belonging to the Codieae, Halimeda, Penicillus, 



