V. RHODOMELACE.E. 55 



short internodes), tessellated with quadrate cells ; axis tubular, articulated, sur- 

 rounded by one or more concentric series of oblong coloured cells, which are suc- 

 cessively shorter toward the circumference ; surface cells quadrate. Ultimate 

 ramidi frequently monosiphonous. Conceptades ovate, terminal, containing a tuft 

 of pear-shaped spores. Teiraspores contained in fusiform, terminal stichidia, in a 

 double row. 



A very natural and now pretty extensive genus, consisting of small Algaj of simi- 

 larly amphibious habits, and all of a dull, blackish or livid purple colour. It is 

 difficult to distinguish some of them by a definite cliaracter from Da.sya, and others 

 from Pol ysipho Ilia ; others again have been placed in RJiodoiuela. They rarely 

 grow in the open sea. Their favourite localities are near high water mark, often 

 in places where they are seldom submerged, or in brackish water, as the estuaries 

 of rivers ; and some grow even in perfectly fresh water, in mountain streams far 

 removed from the sea. The same species, as in the case of B. vaga of Kerguelcn's 

 Land, may occasionally be traced from the rocks and stones about high water mark, 

 to a considerable distance inland. 



The typical species are inarticulate, but are beautifully dotted with large square 

 cells arranged in transverse lines, several cells in each band. Such transverse bands 

 are evidently of the same nature as the many-tubed internodes or articulations of 

 Po/ysipho7ua, the diffei'ence being one of degree, and not of kind, and consisting in 

 the very short and minute cells of the Bostrychia compared to the elongated tubular 

 cells of the Polysiphonia. In other species, as our B. rivularis, the cells of the stem 

 are longer, and the ramuli are almost articulated, the lower parts pluri-striate, their 

 ends unipunctate or monosiphonous. Yet this species cannot be naturally sepa- 

 rated from B. radicans, B. Hooker!, &c. which are of the typical structure ; nor 

 yet again, as I think, from B. Towneyi, which, were there no sucli connecting links, 

 would probabl}' be placed in Dasya. Again, B. calainistrata is in all respects, 

 except in the structure of its ramuli, an orthodox species of Bostrychia ; but by 

 these single-celled ramuli it is associated with the aberrant B. Tourney i. 



Sub-genus 1. Eubostrychia. Peripheric cells in several concentric rows (as seen 

 in a cross section of the stem). 



1. Bostrychia Montagnel; frond ultrasetaceous, opaque ; main stems three or 

 four times pinnated, strongly reflexed or arching backwards ; pinnaj distichous, close 

 together, horizontally patent, recurved, the terminal ones often secund ; pinnules 

 capillary, pinnulate or bipinnulate, dotted, inarticulate, their tips alone unipunctate, 

 surface cells quadrate ; apices inflexed ; stichidia elongate, acuminate. (Tab XIV. 

 B.) 



Hab. On the mangrove stems, at high water mark. Key West, TP^. H. H. Bahia 

 Honda, Prof. Tuomey (9). (v. v.) 



