developed pits in the central strand. As regards its inclusion among the synonyms of H. incrassata^ 

 it is interesting to note the views of Lamouroux and of Dr. Harvey. Lamouroux (Hist. Polyp. 

 Corall. flex. 1816 p. 307), remarks on the presence in the same individual plant of the characters 

 which distinguish H. monile and H. incrassata and suggests that they should at most be reo-arded 

 as only varieties of the same species. This suggestion he repeats in his later work "Exposition 

 Méthodique des genres de 1'ordre des Polypiers", 1821, p. 27, but possibly for want of material 

 to decide the point himself he does not go further and unite the two species. This was however 

 carried out by Dr. Harvev in his Nereis Boreali-Americana (Pt. III. 1858 p. 24.) where H. mcmile 

 is given as a variety of H. incrassata, in consequence of the joints characteristic of the two 

 species being frequently found on one and the same plant, among specimens collected by the 

 author at Key West. 



I have here kept up the name monilis to indicate the form of this species, in which 

 the joints are mostly cylindrical, as figured by Solander (1. c). 



An examination of the type specimens of H. cylindracea Decne. kindly lent me by 

 M. Hariot, ancl of H. polydactilis J. Ag., shew that both these plants are merely forma monilis 

 of H. incrassata. Both of them have well-marked pits in the central strand at the apex of 

 each joint. 



The type specimen of H. triolens (Corallina triolens Eli. et Sol.) is unfortunately not 

 to be found and it is therefore only possible to depend on the original, rather unsatisfactory, 

 figure and the accepted view of later botanists as to the nature of this species. The Kützing 

 figure of H. tridens in Tab. Phyc. 1. c. is an exact representation of the plant under that 

 name in the Kützing Herbarium, now in the possession of Madame Weber-van Bosse. This julant 

 shews the well-developed pits in the central strand and has a long unbranched base, the joints 

 composing it being so thickly calcified as almost to obliterate the divisions between them. This 

 apparent absence of articulation is noticed by Professor J. G. Agardh (Till Alg. Syst. 1. c. p. 87) 

 who wonders what the plant may be from which the Kützing figure is taken. 



The plants under the name of H. tridens in Herbaria are specimens of H. incrassata, 

 as is shewn by their internal structure. The joints of such plants are not often quite so regularly 

 tridentate as in the original figure of Ellis and Solander, which however represents only a 

 fragment. Dr. Harvey remarks of H. tridens Lam. (Ner. Bor. Amer. 1. c.) that it is nearly 

 related to H. incrassata and is perhaps only a variety. The external characters of H. tridens 

 are however not sufficiently distinct from those of forma typica to render it necessary to retain 

 it as a form of variation. 



Among the " Siboga" collections there were plants of H. incrassata indicating lines of 

 variation other than those already known. One of these strongly resembles the trilobed form 

 of H. Opnntia, the joints being markedly tripartite, and the segments thin and cylindrical. This 

 I have called forma tripartita. 



Another form had almost circular joints, strongly resembling those of H. Tuna, forma 

 typica, but differing externally in being faintly ribbed. This I have called forma rotunda. 



Among the already existing varieties of H. incrassata, there is a var. tridentata Duchass. 

 recorded from Guadeloupe. M. Hariot was so kind as to search in the Paris Museum tor the 



