570 RHODOMELACEAE. 



Main branching subdichotomous, commonly fastigiate. 

 Plants 0.5-2.5 cm. high, growing chiefly on leaves 



of Cymodocea, Thahissia, etc. 5. P. Gorgoniae. 



Plants 4-12 cm. high, yellowish or straw-colored 

 when living, vinaceous-tawny to chocolate-col- 

 ored when dry, commonly bearing frequent 

 short subspinescent patent ramuli, clothed with 



numerous trichoblasts. 6. P. hapalacantha. 



Main axes or branches strongly corticated, the main branches 

 virgately clothed with numerous much more slender 



taper-pointed or subspinescent ramuli. 7. P. ramentacea. 



Pericentral cells 8-10, trichoblast few and inconspicuous. 8. P. exilis. 



Pericentral cells 12-24, trichoblasts usually numerous and very 



conspicuous. 9. P. opaca. 



1. Polysiphonia subtilissima Mont. Ann. Sci. Nat. Bot. II. 13: 199. 1840. 



Under shelving rocks, low-littoral. Exuma Chain, and Great Ragged Island : 

 Massachusetts to northern South America. Type from Cayenne, French Guiana. 



2. Polysiphonia havanensis Mont. Ann. Sci. Nat. Bot. II. 8: 352. 1837. 



From between the tide-lines to a depth of 5 meters, found especially on the roots 

 of Rhizophora and in mangrove associations. New Providence, Rose Island, Great 

 Bahama, Cat Island, Watling's Island, Mariguana, Caicos Islands, and Great Ragged 

 Island : Bermuda ; Florida ; and the West Indies generally. Type from Havana. 



3. Polysiphonia Binneyi Harv. Xer. Bor.-Am. 2: 37. 1853. 



Polysiphonia havanensis Binneyi J. Ag. Sp. Alg. 2: 960. 1863. 



In shallow water, possibly intergrading with P. havanensis, but usually very 

 distinct, New Providence, Berry Islands, Joulter's Cay, Great Bahama, Exuma Chain, 

 Watling's Island, Mariguana, Caicos Islands, and Great Ragged Island : Florida. 

 Type from Key West, Florida. 



4. Polysiphonia ferulacea Suhr; J. Ag. Sp. Alg. 2: 980. 1863. 



Polysiphonia breviarticulata Harv. Xer. Bor.-Am. 2: 36. pl.l6B. 1853. Not 

 Hutchinsia breviarticulata Ag. Syst. Alg. 153. 1824. 



Usually low-littoral on surf-beaten rocks, New Providence, Berry Islands, 

 Joulter's Cay, Great Bahama, Gun Cay. Watling's Island, Atwood Cay, Mariguana, 

 Caicos Islands, and Little Inagua : Bermuda ; Florida ; Mexico ; and the West In- 

 dies generally. Type locality unknown, probably West Indian. 



5. Polysiphonia Gorgoniae Harv. Ner. Bor.-Am. 2: 39. 1853. 



On Cymodocea, Thalassia, corals, sea-fans, and occasionally on the larger algae, 

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

 Watling's Island, Mariguana, and Great Ragged Island : Florida. Type from Key 

 West, Florida. 



6. Polysiphonia hapalacantha Harv. Xer. Bor.-Am. 2: 39. 1853. 



In shallow water, Great Bahama and Exuma Chain : Florida. Type from Key 

 West, Florida. 



7. Polysiphonia ramentacea Harv. Xer. Bor.-Am. 2: 42. pi. 16 A. 1853. 



Related to P. foenictdacea (Drap.) J. Ag. and P. hirta J. Ag. of the Mediterra- 

 nean Sea, but differing considerably in its virgate habit due to the closely set ramuli 

 of nearly uniform length, becoming gradually shorter at apex. On rocks and other 

 algae from low-water mark down to a depth of at least two meters, New Providence, 

 Berry Islands, Great Bahama, Exuma Chain, and Little Inagua : Florida. Type 

 from Key West, Florida. 



8. Polysiphonia exilis Harv. Xer. Bor.-Am. 2: 47. 1853. 



Lophosiphonia ? exilis De-Toni, Syll. Alg. 4: 1070. 1903. 



Near low-water mark and on sea-fans in shallow water, New Providence, Rose 

 Island, and Great Ragged Island : Florida. Type from Key West, Florida. 



