62 BATRACHOSPERME^. 



streams) on which it grows. The plants referred to this Order naturally group 

 themselves into two suborders, distinguished from each other by the habit of the frond 

 but closely related in structure and fructification, and as it seems to me inseparably 

 connected by the genus Tuomeya, which unites in itself the characters of the seemingly 

 so dissimilar genera Batrachospermum and Lemanea. In the first suborder (Batra- 

 chospermece verce) the branching filiform frond consists of a solid axis, invested with a 

 gelatinous coating, and composed of vertical, confervoid filaments, strongly glued 

 together. This axis is either, as in Batrachospermum, whorled at short intervals with 

 moniliform ramelli, formed of globose cellules strung together ; or else, as in Thorea, 

 it is uniformly clothed with a villous stratum of byssoid ramelli, formed of cylindrical 

 cellules. The fructification, so far as known in this suborder, consists of globular, very 

 dense tufts of spore-threads, similar in structure to the ramelli, but of more minute 

 size, and far more densely packed together. I question whether they be properly spores^ 

 probably they are rather highly developed or compound gemmae. In the second sub- 

 order, Lemaniece, the frond is denuded of confervoid ramelli, and consists altogether of 

 a compound, filiform axis, composed of minute cells. In Lemanea the frond is hollow 

 and tubular, the walls of the tube being laxly constructed within ; and moniliform 

 strings of spores, similar to those of Batrachospermum, are attached to the surface of 

 the tube. This structure is almost the exact reverse of that of Batrachospermecje, 

 where the central axis is most solid, and clothed externally with moniliform filaments. 

 In Tuomeya the frond has at first the external characters of a Lemanea, but is furnished 

 with an axis having the structure of a Batrachospermum, as if a Batrachospermum 

 were developed within the tube of a Lemanea ; and when fully developed the surface is 

 uniformly coated with minute filaments, as in Thorea. 



Authors differ much in their views of the proper limits of this Order, Decaisne 

 unites with it Liagora and Dichotomaria (Galaxaura) both of which are undoubtedly 

 Rhodosperms ; and Myrioclaclia, which is a Melanosperm. Kiitzing separates Batra- 

 chospermum as the type of an Order of which it is the only genus ; while he refers 

 Galaxaura, Aetinotrichia and Lemanea to his Lemanieae ; and places Thorea with his 

 Chffitophorideae. My own views more nearly correspond with those of Mr. Berkeley, 

 who brings Batrachospermum, Thorea, and Lemanea together into one Order. These 

 genera are exclusively fluviatile or lacustrine, so far as I am aware. The marine 

 variety ^^ purpurascens," Roth, oi Batr. moniliforme is founded on a figure of Dillenius 

 (Hist. Muse. t. l.fig. 40j which certainly looks very like a Batrachospermum, but the 

 original specimen preserved in the Dillenian Herbarium belongs, according to Turner, 

 to Ceramium diaphanum. The marine " Thorea Americana" of Kiitz. is assuredly 

 not a congener with T. ramosissima, the type of the genus ; but properly referred by 

 Bory, who first described it, to Chordaria. 



Like most fresh water Algaj, several of the species are widely distributed. Batra- 

 chospermum moniliforme is found throughout Europe in various parts of Asia, in Tas- 

 mania and New Zealand, and in extra-tropical South America ; and B. vagum and 

 atrum, of which as yet I have seen no North American specimens, have nearly as exten- 

 sive a range. Lemanea torulosa occurs in Europe. Tuomeya fluviatilis has only as 

 yet been found in North America, but occurs in distant localities (New York and 

 Alabama) and may probably be found to have a much larger area of distribution. 



