596 DICTYOTACEAE. 



4. DICTYOTA Lamour. Xouv. Bull. Sci. Soe. Philorn. 1: 331. My 1809. 



Jour, de Bot. 2: 38. 1809. 



Branching more or less regularly dichotomous. 



Segments mostly 15 mm. broad, the apical obtuse, patent or suberect. 



Segments linear, the dichotomies usually 1-2 cm. apart. 1. D. dichotoma. 

 Segments oblong, the dichotomies usually 0.51 cm. apart. 2. D. Bartayresii. 

 Segments mostly 0.31 mm. broad, the apical acute, acuminate 



or subobtuse, divaricate or subdivaricate. 3. D. divaricata. 



Branching dichotomo-pinnatifid or cervicorn. 



Branching cervicorn, or dichotomo-subpinnate below and 

 dichotomous above ; segments narrowly ribbon-shaped, 

 mostly 0.5-1 mm. broad, often proliferous along the middle, 

 the apical segments acute or subobtuse, sometimes sub- 

 terete or subconic, mostly patent. 4. D. cervicornis. 

 Branching dichotomo-pinnatifld, main segments or axes mostly 

 2-5 mm. broad, the apices usually acuminate, sometimes 

 obtuse. 5. D. dentata. 



1. Dictyota dichotoma (Huds.) Lamour. Xouv. Bull. Sci. Soe. Philom. 1: 331. 



My 1809. 



Ulva dichotoma Huds. Fl. Angl. 476. 1762. 



From near low-water mark down to a depth of several meters. Rose Island, 

 Berry Islands, Bimini, Exuma Chain, Watling's Island, Atwood Cay, Mariguana, 

 Caicos Islands, and Great Ragged Island : Bermuda, North Carolina, Florida and 

 West Indies : widely distributed in temperate and tropical seas. Type from Isle of 

 Walney, England. 



2. Dictyota Bartayresii Lamour. loc. cit. 



Dictyota Bartayresiana Lamour. Jour, de Bot. 2: 43. 1809 1 . 

 Dictyota patens J. Ag. Till Alg. Syst. 2: 93. 1882. 



Common, mostly in shallow water, often slightly iridescent when living. New 

 Providence, Rose Island, Berry Islands, South Cat Cay, North Cat Cay, Eleuthera, 

 Watling's Island, Atwood Cay, Mariguana, Caicos Islands, and Great Ragged Island : - 

 West Indies. Type from Santo Domingo (?). 



The type specimen (in " Zonaria dichotoma" cover in herb. Lamour. at Caen) 

 has segments 2-5 mm. broad and obtuse apices. Specimens with acute and acuminate 

 apices referred to this species by later writers are to be looked upon as probably 

 representing the more dichotomous ov less pinnate conditions of D. dentata. 



3. Dictyota divaricata Lamour. loc. cit. 



In shallow water. New Providence, Berry Islands, Great Bahama, North Cat 

 Cay, Exuma Chain, and Caicos Islands : West Indies and warmer seas generally. 

 Type from the Mediterranean. 



Apparently intergrades with D. cervicornis, D. intlica, and D. Bartayresii. 



4. Dictyota cervicornis Kiitz. Tab. Phyc. 9: 11. pi. 24. f. II. 1859. 



Dictyota, Fasciola Harv. Xer. Bor.-Am. 1: 108. pi. 8B. 1852. Not Fucus 

 Fasciola Roth, (=Dilophus repens J. Ag.). 



On rocks near low-water mark in rather exposed situations. New Providence, 

 Rose Island, Berry Islands, Great Bahama, Gun Cay, Exuma Chain, Mariguana, 

 Caicos Islands, and Little Inagua : Bermuda, Florida, and probably West Indies 

 in general. Type from Key West, Florida. 



Often proliferous near the middle line of thallus and easily confused with 

 Diloiilius uitini-cimis which is rather similar both in general habit and in tendency to 

 proliferate. 



5. Dictyota dentata Lamour. Xouv. Bull. Sci. Soe. Philom. 1: 331. My 1809. 



Fucus atomarius S. G. G'mel. Hist. Fuc. 125. pi. 10. f. 1. 1768. Xot D. 



Atomaria Grev. Xot Dictyota Atomaria Hauck. 

 Ulva Mertensii Mart. Fl. Bras. Aeot. 21. 1833. 

 Dictyota Brongiartii J. Ag. Linnaea 15: 5. 1841. 

 Dictyota Mertensii Kiitz. Tab. Phyc. 9: 15. pi. 36. f. 1. 1859. 

 Dictyota subdentata Kiitz. loc. cit. 14. pi. 33. f. II. 



On rocks in shallow water. New Providence, Berry Islands, Great Bahama, 

 North Cat Cay, Gun Cay, Atwood Cay, Mariguana, Caicos Islands, and Great 

 Ragged Island : Bermuda and Florida to Brazil. Type from the Antilles. 



