108 L. HILLIS-COLINVAUX 



The limited nodal material of borneensis I have been able to examine 

 showed firm fusion of all the medullary filaments into a single unit for 

 a short distance with well-developed pores. I did not find the filaments 

 to separate more readily than in other Rhipsalian species, although 

 Taylor (1975) reported a very light fusion, with filaments separating 

 easily. 



Halimeda macroloba Decaisne 



Figure 28. 



Halimeda macroloba Decaisne (1841), p. 118; Decaisne (1842), p. 91; Barton 

 (1901), p. 24, Plate 3, Figs 33-38; Hillis (1959), p. 375, Plates 3, 5, 6, 12. 

 Halimeda macroloba v. ecalcarea Weber-van Bosse (1926), p. 88. 



Plants erect, flat or somewhat bushy, to 23 cm tall excluding the holdfast 

 which is usually well developed and may extend to 5 cm in length ; calcification 

 moderate to rather light; branching relatively sparse, mainly ditrichotomous 

 but often becoming polychotomous in the basal region; basal segments 

 commonly compressed- cylindrical to trapezoidal, of a somewhat stipitate 

 nature and supporting several segments which may remain separate or 

 consolidate laterally, either entirely or in part, to form a fan- shaped unit 

 which may lie flat or become somewhat undulated or folded ; other segments 

 plane or slightly ribbed, at times compressed- cylindrical but more commonly 

 subcuneate, discoidal or subreniform, the upper margin entire, undulating or 

 occasionally somewhat lobed, to 29 mm long, 40 mm broad and averaging 

 1 mm in thickness. 



Cortex occasionally of two, but more commonly of three to four layers 

 of utricles; outermost utricles separating on decalcification or remaining 

 slightly attached, their lateral and peripheral margins occasionally 

 thickened, 23-49 [im. in surface diameter, (46-)62-110(-144) iim long in 

 section, usually four or occasionally two supported by each secondary 

 utricle; secondary utricles 20-58(-68) fjim broad, (30-)40-80(-140) [xm long; 

 tertiary utricles 36-90(-110) [xm broad. 



Nodal medullary filaments uniting as a single group for a distance of 

 approximately 44-80(-115) [xm, the adjacent filaments communicating by 

 pores ; walls in this region thickened and pigmented. 



Type specimen. Red Sea, Schimper 871, 1837; isotype material 

 in several herbaria including the British Museum (Natural History) 

 and the New York Botanical Garden. 



Habitat. Grows in mud or other unconsolidated substrate, from 

 above low -tide line to —12 m, sometimes developing extensive 

 stands in the shallows. Its holdfast may also be associated with bits 

 of coral rock and is then smaller. It often grows in the quiet waters 



