Some confusion has existed in herbaria between this species and H. Tuna forma platydisca. 

 They may be distinguished, however, externally by the thickness and the smooth, shining appearance 

 of the joints in H. macroloöa, which are rather more deeply calcified than the thin joints of 

 H. Tuna forma platydisca. 



As regards internal structure, the mode of fusion of the central filaments is entirely 

 different from that of H. Tuna. In H. macroloöa the filaments do not fuse, but communicate with 

 each other at the point of contact by means of pits in their walls. These pits are so large that 

 the whole strand has almost the appearance of one large tube with the bounding wall against 

 the peripheral cells. This is clearly to be seen in a surface view of the growing point or in a 

 transverse section of the apex of any joint, where the central filaments appear as one, with 

 the original boundaries of the separate tubes only marked by the fragments of the side walls 

 still remaining. Communication between the filaments is however limited to this point ; above 

 it each filament is free, and after a short distance branches, generally trichotomously, to aid 

 in the formation of the next joint. 



The branching in H. macroloöa takes place in one plane, but I have seen in one plant 

 indications of a joint growing out at right angles from the face of another joint, as in H. Opuntia. 



The geographical distribution of H. macroloöa is not wide, the species being almost 

 entirely confined to the Indian Ocean. A few records only have been made from the Pacific Islands. 



. j. H. incrassaia Lam. 



"Sur 1. Classif. d. Polyp. Corall. etc." in Soc. Phil. N. Buil. Paris III. 1812. p. 186. 

 Lichen marinus rotundifolius Buddle, M. S. in Herb. Sloane. vol. 114 — 116, fol. 137. 

 Articulated Coralline of Jamaica Ellis, Essay Nat. Hist. Corallines 1755. p. 53. PI. XXV. figs. A. a. 

 Corallina incrassata Ellis and Solander, Xat. Hist. Zoophytes 1786. p. 111. Tab. 20. fig. d. 

 Flabellaria incrassata Lamarck, "Sur 1. Polypiers empatés" in Ann. Mus. Hist. Xat. torn. 20. 



1813. p. 302. 

 Halimecla incrassata Lamouroux, u Sur 1. Classif. d. Polyp. corall. etc." in Soc. Phil. N. Buil. 



Paris III. 18 12. p. 186. 

 Halimeda incrassata Lamouroux, Hist. Polyp. corall. 18 16. p. 307. 

 Halimeda incrassata Lamouroux, Expos. méth. 182 1. p. 26. Tab. 20. figs. D. d. 

 Halimecla incrassata Lamouroux, Corallina 1824. p. 139. 

 Halimeda incrassata Decaisne, Mém. s. 1. Corall. in Ess. Class. Alg. et d. Polyp. Calcif. 



1842. p. 91. 

 Halimeda incrassata Kützing, Phyc. Gen. 1843. p. 310. 

 Halimeda incrassata Kützing, Spec. Alg. 1849. p. 504. 

 Halimeda incrassata Harvey, Xereis Bor. Americ. 1858. Pt. III. p. 24. 

 Halimeda incrassata Harvey, Phyc. Austr. vol. III. 1860. PI. CXXV. 

 Halimeda incrassata J. G. Agardh, Till. Alg. Syst. VIII. p. 85 et vars. 

 Halimeda incrassata Askenasy, Forschungsreise S. M. S. Gazelle Th. IV. Bot. Algen. 1888. 



p. 13. Tab. III. figs. 1, 7. Tab. IV. figs. 5, 6, 10. 

 Halimeda incrassata et vars. De Toni, Syll. Alg. vol. I. 1889. p. 522. 

 Corallina monile Ellis and Solander, Xat. Hist. Zooph. 1786. p. 1 10. Tab. 20. fig. c. 

 Halimeda monile Lamouroux, "Sur 1. Classif. d. Polyp. corall. etc." in Soc. Phil. X. Buil. Paris 



III. 1812. p. 1S6. 

 Halimeda monile Lamouroux, Hist. Polyp. Corall. 18 16. p. 306. 

 Halimeda monile Lamouroux, Expos. Méth. 1821. p. 26. Tab. 20. fig. c. 

 Halimeda monile Lamouroux, Corallina 1824. p. 138. 



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