CERAMIACEAE. 579 



5. Spermothamnion gymnocarpum M. A. Howe, sp. now 



Indian lake or purplisli-vinaceous, fading to brownish-vinaeeous, grayish- 

 vinaceous, or vinaceous-fawn, forming rather dense cushions 1-3 cm. deep or 

 somewhat straggling in habit ; primary creeping filaments 50-130 /jl in diameter, 

 their cells 130 400 fi long, mostly 3-5 times as long as broad, their walls 13-50 (i 

 thick, the erect branches arising mostly from near the end of the cell ; erect 

 filaments 50-115 /j. in diameter, rather freely subdichotomously, alternately, or 

 subseeundly branched, rarely with 3 or 4 branches at a node, the branches patent 

 or erecto-patent, arising subterminally or laterally just below the septum, the 

 cells 300-750 m long, mostly 3-7 times as long as broad, cylindric or slightly 

 enlarged at upper end, the walls 5-40 fi thick, the terminal cells 40-65 fi in di- 

 ameter, obtuse, or in the more branched conditions often only 12-15 /j. in diam- 

 eter with walls only 1-2 fi thick; chromatophores suborbicular, elliptic, fusiform, 

 substellate, or diff orm, more or less confluent discs 2-13 n in maximum diameter ; 

 monoieous (polyoicous ?) ; procarps and cystocarps solitary or several closely 

 approximate ; procarps subglobose or hemispheric, 40-50 /x broad, the trichogyne 

 10-13 ij. in diameter; cystocarps moriform or irregularly hemispheric, 80-150 fj. 

 broad, wholly destitute of an involucre ; antheridial stands ovoid to subcylin- 

 dric, 40-80 fi X 26-40 ii; tetrasporangia borne on one-celled pedicels at nodes 

 in distal parts of the main erect filaments and their branches, solitary or more 

 often 2-5 at a node and aggregated on the inner side, or subverticillate, sub- 

 globose, 60-80 /jl in diameter, their walls 5-12 /m thick. 



On and with various other algae (Junta, Laurencia, Chamaedoris , etc.), in shal 

 low water and washed ashore, Great Bahama (Hoicc 3879 type) and Exuina Chain. 



The species is perhaps related to the European S. irregulare (J. Ag.) Ardiss., 

 but manifestlv differs in its longer, less ventricose cells, naked cystocarps. etc. Most 

 of the few antheridial stands seen have been very close to the procarps, but the 

 procarps preponderate so much in number that it may be suspected that dioicous 

 conditions also occur. 



2. MESOTHAMNION Borg. Dansk Bot. Ark. 3': 208. 1917. 



1. Mesothamnion caribaeum Borg. loc. cit. 



The single Bahamian specimen seen is sterile and the determination is 

 open to possible doubt. It is 0.5-1 cm. high and is remarkable for its penicil- 

 lately tufted apices, the lower parts of the main axes being more or less 

 denudate. 



On Gelidium rigid urn, near low-water mark, Gun Cay : American Virgin Islands. 

 Type from St. Jan (dredged in 30 meters of water). 



3. G-RirFITHSIA Ag. Syn. Alg. Scand. xxviii. (as Griffitsia). 1817. 



Branching mostlv subdichotomous, the branches issuing from the 



upper end of the parent cell. 1- G. !ilinihfera. 



Branching distinctly lateral, the branches issuing from near the 



middle or below the middle of the parent cell. - G. tenuis. 



1. Griffithsia globulifera Harv.; Kiitz. Tab. Phyc. 12: 10. pi. 30. f. a-d. 1862. 



Griffithsia coraUina gloUfera Harv. Ner. Bor.-Am. 2: 228. pi. S5A. 1853. 



< i rifHtlisia coraUina tenuis Harv. loc. cit. 



Griffithsia gloUfera Harv.; J. Ag. Sp. Alg. 3 1 : 67. 1876. 



Griffithsia Bornetiana Farl. Proc. Am. Acad. 12: 243. 1877. 



The Bahamian plants referred here seem to agree essentially with the 

 northern type in the character of the antheridia, cystocarps, and tetrasporangia, 

 but they are smaller plants and the filaments are often more moniliform, these 

 differences being especially manifest in sterile and more doubtful specimens 

 ihat have been identified tentatively with this species. The plants occur on surf- 



