86 L. HILLIS-COLINVAUX 



Section Halimeda J. Ag. ex De Toni 1889 as Tunae. 



Filaments of a node most commonly fusing in both twos and threes ; 

 units occasionally may be larger, or filaments may remain single; 

 fusion short or complete depending on the species. 



Section Micronesicae n. sect. 



Filaments of a node remaining completely separate, or a few may 

 be joined briefly in H. melanesica. 



Section Crypticae n. sect. 



Single medullary filament unchanged at the node. 



Latin diagnoses for new sections 



Section Micronesicae 



Filamenta nodi omnino discreta manentia, vel, in H. melanesica, 

 aliquot interdum curte conjuncta. 



Section Crypticae 



Unicum filamentum medullosum ad nodos immutabile. 



E. Taxonomic hey to all species, and list of Indo- Pacific species 



1. Composite hey to all species 



1. Plants growing in sand or other loose substrates; holdfast usually 

 well developed, rarely less than 1 cm long and frequently massive ; 

 nodal medullary filaments uniting into a single group, the adjacent 

 filaments usually communicating by pores . . . section Rhipsalis . . 2 



1. Plants generally attached to rock, or if associated with sand 

 lacking a well-developed bulbous holdfast; holdfast rarely 

 exceeding 1 cm in length, although sometimes it may spread 

 laterally to this size or somewhat larger; more than one holdfast 

 region may be present; nodal medullary filaments remaining 

 separate or uniting in twos, threes and occasionally fours. . .. 10 



2. Segments large, broad, flat, to 29 mm long and 40 mm broad . . 3 



2. Segments smaller, flat or cylindrical, to 12 mm long and 16 mm 

 broad (excluding basal or fusion segments) . . . . . . 5 



3. Segments predominantly large, subcuneate to reniform and little 

 lobed, to 29 mm long, 40 mm broad ; fan-shaped basal or 

 suprabasal segment absent (Fig. 27); peripheral utricles some- 

 times separate and round . . . . . . H. macroloba, p. 108 



3 Segments rarely exceeding 12 mm long and 17 mm broad, margins 

 often crenulated or lobed; if peripheral utricles separate on 

 decalcification they remain hexagonal . . . . . . . . 4 



