RHODOMELACEAE. 521 



of a brownish- or violet-red color. It has been found in Hamilton Harbor and 

 near Hotel Frascati. (Phyc. Bor.-Am. 1890.) 



Polysiphonia opaca (Ag.) Zan. has 14-20 pericentral siphons and the 

 median segments mostly 1-14 times as long as broad. It is commonly 2-5 

 inches high and is of a brownish color, darkening with age. It grows in 

 tide-pools on the South Shore, on rocks at Tucker's Town, etc. (Phyc. Bor.- 

 Am. 1891.) 



Herposiphonia tenella (Ag.) Ambronn, is rather common, creeping on 

 Halimeda, Udotea, Sargassum, etc. and on roots of JRhizophora. In habit, due 

 chiefly to the length of its "short" branches, it varies greatly according to 

 habitat, these branches being 20-50 segments long in the form on Khisophora 

 and mostly 12-25 segments long in the forms on algae, but intermediates ap- 

 parently occur. The Herposiphonias differ from the Polysiphonias in their 

 creeping habit, dorsiventral organization, the dorsally recurved and inrolled 

 apex, and the "short" branches alternating in two regular dorsal rows. In 

 both this species and the next, the segments show 8-10 pericentral siphons 

 and are mostly 1-2 times as long as broad. In the present species there is a 

 branch of some sort at nearly every node of the main axes, complete regularity 

 being interfered with occasionally by suppression or abortion. (Phyc. Bor.- 

 Am. 1943.) 



Herposiphonia secunda (Ag.) Ambronn, like the preceding, usually creeps 

 on various algae (Sargassum, Laurencia, etc.). It is best distinguished by the 

 less frequent branches, these commonly occurring at every third or fourth 

 node. The "short" branches are usually shorter than in the preceding, being 

 mostly 7-20 segments long. (Phyc. Bor.-Am. 2041.) 



Lophosipsonia obscura of current writers [not Hutchinsia obscura Ag;.,* 

 which is Lophosiphonia svbadunca (Kiitz.) Falkenb.] is rather common, form- 

 ing dense felted mats about half an inch deep on rocks near the high-water 

 mark. The primary axes creep, somewhat as in Herposiphonia, but the 

 branches are less regular in their origin and development; the branches are 

 endogenous in origin and are not laid down in a regular exogenous series at 

 the apex of the main axis as in Herposiphonia. The Bermuda plant commonly 

 has 10-12 pericentral siphons and its segments are mostly about as long as 

 broad. The current specific name, though invalid, is here used, pending 

 further studies of its synonymy. (Phye. Bor.-Am. 1892.) 



Lophosiphonia Saccorhiza Collins & Hervey, is a new name that has 

 recently been given (Phyc. Bor.-Am. 2042) to a minute 4-siphoned plant that 

 creeps on and among the utricles of Codium. It occasionally shows free parts 

 that suggest the genus Polysiphonia rather than Lophosiplionia. Polysiphonia 

 codiicola Zan. is perhaps a close relative. 



Dipterosiphonia rigens (Schousb.) Falkenb. (Lophosiphonic bermudensis 

 Collins & Hervey). This is a minute plant that creeps on Sargassum, Lau- 



* Diatoms that coated Agardh's type specimen and obscured its structure are 

 apparently responsible for this specific name. 



