430 



BULLETIN OF THE BUREAU OF FISHERIES. 



Gomontia polyrhiza (Lagerheim) Bornet and Flahault. Fig. 4. 

 CodMum polyrhizum, Lagerheim, 1885, p. 21, pi. 28. 

 Gomontia polyrhiza, Bornet and Flahault. i888a. p. 163. 

 Gomontia polyrhiza, Bornet and Flahault, 1889. p. CLII. pis. 6-8. 

 Gomontia polyrhiza, De Toni, 1889, p. 389. 

 Gomontia polyrhiza, Collins. 1909, p. 37O. pi. 15. f- I3S- 

 P. B.-A. No. 315- 



Filaments 4 to 8 mic. in diameter; sporangia 30 to 40 mic. in diameter; zoospores of two sorts, one 

 loto 12 by 5 to 6 mic., the other about 5 by 3.5 mic.; development not known; the smaller ones possibly 

 gametes(?); aplanospores 4 mic. in diameter. 



Abundant on both coasts of North America; Europe. 



In shells, Pamlico Sound, Ocracoke, N. C., August, 1907. 



Order 3. Siphonales. 



Fronds filiform, usually much branched or interwoven into various forms, usually 

 continuous without dissepiments in the vegetative condition, multinucleate, with many 

 lens or disk shaped chromatophores. 



The members of this order are, with few exceptions, marine and are mostly confined 

 to tropical and warm temperate regions. 



KEY TO FAMILIES. 



a. Frond differentiated into root, stem, and branches of varied form .4. CAULERPACE^S (p. 434). 



oo. Frond not differentiated into root, stem, and branches 7 b. 



b. Filaments interwoven to form fronds of definite form 3. CODIACE^B (p. 431). 



66. Filaments branching, plumosely, not interwoven 2. BRYOPSIDACE^ (p. 431). 



666. Filaments branching dichotomously or irregularly, forming indefinite mats 



i. DERBESIACE^E (p. 430). 



Family 1. DERBESIACE/E Thuret. 



Vegetative frond mostly unicellular, irregularly or dichotomously branched, forming 

 indefinite mats, or consisting of upright branches arising from creeping filaments attached 

 to the substratum by short, irregular branches; chromatophores large or small disks, 

 each containing i to 3 pyrenoids, or lacking these; asexual propagation by means of 

 almost spherical zoospores, formed (8 to 20) in sporangia arising as lateral branches of 

 definite shape and cut off from the main filaments by cross walls, each zoospore possessing 

 a circle of cilia and germinating immediately; sexual reproduction unknown. 



About nine species, all marine, in North America, Europe, and Asia. 



Genus Derbesia Solier. 

 Derbesia, Solier, 1847, p. 157. 



Characters of the family. 

 About nine species. 

 Derbesia turbinata Howe and Hoyt. PI. CXV, figs. 10-16. 



Derbesia turbinata, Howe and Hoyt, 1916, p. 106, pi. . figs. 10-16. 

 Derbesia turbinata, Collins, 1918, p. 92. 



Frond more or less creeping, forming straggling mats 8 to 9 cm. broad (or high?) the basal parts some- 

 times here and there resolved into cysts; filaments 16 to 100 mic. (mostly 40 to 55 mic.) in diameter, 

 sparingly branched, the branching subdichotomous or more often lateral, the lateral branches usually 

 without a basal septum, the others with or without one or two septa above the dichotomy; chloroplasts 

 at first orbicular elliptic or ovate, 5 to 7 mic. in diameter, later irregularly confluent and spindle 

 shaped; zoosporangia turbinate, broadly obconi-obovoid, broadly pyriform, or pestle shaped, 137 to 



