386 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



Family i. CODIACEAE. 



Frond except in the lowest forms of definite shape, composed 

 of interwoven, continuous, branching filaments, sometimes ap- 

 parently pluricellular by constrictions, calcified or not.. Asex- 

 ual reproduction by zoospores and aplanospores, formed in spo- 

 rangia ; sexual reproduction by zoogametes, the sexes either 

 similar or differing in size. 



KEY TO THE GENERA OF CODIACE'AE. 



i. Not calcified nor stipitate, soft and spongy ; cortical layer formed of 

 the s\vollen ends of the longitudinal filaments. Subfamily COD- 

 IOIDEAE. i. CODIUM. 



i. Stipitate or of seriate disks, often calcified ; cortical layer, when 

 present, formed of lateral branches, usually smaller than the 

 longitudinal filaments. Subfamily UDOTOIDEAE. 2. 



2. Frond terminating in a penicillate tuft of free filaments. 



2. Frond not terminating in free filaments. 3. 



3. Frond of a branching series of disks. 7. HAUMEDA. 



3. Disks terminal or wanting. 4. 



4. Frond terminating in numerous flat expansions. 



4. RHIPOCEPHALUS. 



4. Frond not terminating in numerous flat expansions. 5. 



5. No definite cortical layer. 2. AVRAINVII^LEA. 



5. Cortex present either on stipe or lamina. 6. 



6. Cortex of divaricate, labyrinthiform branches always present. 



6. CLADOCEPHALUS. 



6. Cortex of lamina wanting, or of short, little divided branches. 



5. UDOTEA. 



Subfamily CODIOIDEAE. 

 i. CODIUM Stackhouse, 1795, p. XVI. 



Frond of spongy texture, of very varying form, consisting of 

 branching, continuous filaments, their swollen ends, " utricles " 

 closely packed to form a cortical layer ; sexual reproduction by 

 zoogametes, produced in subovoid sporangia, borne laterally on 

 the utricles ; large biciliate female gametes produced in spo- 

 rangia with very dark green contents ; small biciliate male 

 gametes produced in sporangia with yellowish contents; male 

 and female usually produced on distinct individuals, but occa- 

 sionally on the same individual ; by the union of the two sexes 

 a zygote is produced, germinating immediately ; no asexual 

 reproduction is known, but is probable that female zoospores 

 sometimes germinate parthenogenetically. 



The species of Codinin here recognized are based either on ex- 

 ternal form, which is more or less variable in each species, or on 



