THE MARINE ALG^ OF NEW ENGLAND. 149 



On rocks at low-water mark. 



Common from New York northward. 



The coimnou Irish moss which is used, for culinary purposes, and also for clarifying 

 Leer. It is also said to be used in the manufacture of cheap cotton cloths. Although 

 very variable iu shape, it is not likely to be mistaken for any other species, except 

 possibly sterile specimens of Gigartina mamiUaris or Gymnqgongrus Norveglcus, which 

 is, however, a rare species. When growing exposed to the light, the color is a yel- 

 low-green. 



Suborder RHODYMENIE^E. 



Fronds membranaceous or filiform, solid or tubular ; antheridia form- 

 ing superficial patches ; tetraspores tripartite, cruciate, or zonate, either 

 scattered in distinct spots or sometimes sunk in crypts ; cystocarps ex- 

 ternal, containing- densely packed subdichotomous filaments, arranged 

 in distinct masses around a basal placenta with a thick pericarp, which 

 is connected by numerous filaments with the placenta. 



The present suborder is exceedingly ill-defined, and no two writers agree exactly as 

 to its limits. In the typical genera we find a distinct basal placenta on which are 

 borne masses of spores, which when young are seen to be formed of subdichotomous 

 filaments, but which when mature are arranged without order and held together by a 

 gelatinous envelope. Diverging from the type, we have genera like Cordylecladia, in 

 which, even at maturity, the spores preserve to a certain extent a moniliform arrange- 

 ment, and we then have a cystocarp but little different from that of Gracilaria, which 

 belongs to the Sphccrococcoidetv.. On the other hand, we have the order connected with 

 the Crypionemiea; by Chrysymenia, which is now placed by Agardh in the Iihodymeniaeece. 

 The position of Ekodophyllis and Euihora is doubtful. Here we have no distinct basal 

 placenta, but rather a central placenta or carpogenic cell, reminding one somewhat of 

 the genus Iihabdonia and i ts allies, which have been included in the Solieriece. Euihora, 

 at any rate, demands a more accurate study, and our own species of Iihodophyllis, R. 

 veprecula, does not well correspond with the typical members of the suborder in rela- 

 tion to its cystocarpic fruit. Lomentaria and Champia agree with the Ehodymeniece in 

 their fruit, although the fronds are peculiar, and we have kept them as a division of 

 the present. 



Tribe I. Rhodymenie^e proper. 



Cystocarps with a basal placenta, fronds solid. 



Fronds dichotomous or palmate Bhodymenia. 



Fronds pinnately compound Plocamium. 



Fronds filiform Cordylecladia. 



% Tribe II. Rhodophylleje. 



Cystocarps with a central placenta, fronds membranaceous. 



Tetraspores zonate, fronds dichotomous or pinnate BJiodophyllis. 



Tetraspores cruciate, frouds dentato-pinnate Eutlwra. 



Tribe III. Lomentarie^e. 



Cystocarps with a basal placenta, fronds tubular. 



Fronds constricted at the joints, but with no proper diaphragms, tetra- 

 spores sunk in depressions of the frond Lomentaria. 



Fronds with numerous diaphragms, tetraspores superficial Champia. 



