forms and, at the same time, have characteristics by which a person can tell 

 them apart with the naked eye. Group descriptions are given for the different 

 kinds that cannot be told apart without a hand lens or microscope or are with- 

 out flowers or seeds. 



50. HUMM, H.J. , "Seagrasses on the Northern Gulf Coast," Bulletin of Marine 

 Saienae, Vol. 6, No. 4, Dec. 1956, pp. 305-308. 



Observations in Mississippi Sound indicate that at least five species of 

 marine monocotyledonous plants occur in abundance along the northern gulf 

 coast and may be virtually continuous between Florida and Aransas, Texas. An 

 annotated list of species and a key are included. 



51. HUMM, H.J., "Epiphytes of the Seagrass, Thatassia testudinuniy in Florida," 

 Bulletin of Marine Science, Vol. 14, No. 2, June 1964, pp. 306-341. 



A total of 113 species of algae are reported occurring as epiphytes on the 

 seagrass, Thalaseia testudinum, 92 of which have been recorded from the south 

 Florida area, 20 to 25 percent of the total algal flora. Two groups of epi- 

 phytes are recognized, the year-round species and the seasonal annuals. Among 

 the year-round species are calcareous Corallinaceae which contribute signifi- 

 cantly to the sediments of seagrass beds; the seasonal annuals are a group of 

 large plants which may become sufficiently abundant during winter and spring 

 to shade the T. testudinum significantly. Each species is annotated, and a 

 key to the species known to occur as epiphytes on T. testudinum in south 

 Florida is provided. Stiatyosiphon ssp. and Potysiphonia harVeyi are newly 

 reported for Florida; Gviffithsia bavbata is newly reported for the Bahamas. 



52. HUMM, H.J., "Seagrasses," Proceedings of Marine Environmental Implications 

 of Offshore Drilling in the Eastern Gulf of Mexico, R.E. Smith, ed. , State 

 University System of Florida, Institute of Oceanography, St. Petersburg, 

 Fla., Mar. 1974, pp. 149-151. 



Florida's gulf coast has seagrass beds that extend 10 miles or more out on 

 the gently sloping Continental Shelf. Three species (^Thatassia testudinum, 

 Syringodium filiforme, and Ealodule wrightii) make up 99 percent of the bio- 

 mass of these beds. Three other species occur but in smaller quantity or a 

 more limited distribution. Seagrasses are important primary producers, 

 exceeding the productivity of phytoplankton in the areas they occupy, and they 

 also provide an essential environment for many species of invertebrates and 

 fishes. 



53. JAGELS, R., "Studies of a Marine Grass, Thalassia testudinum I., Ultra- 

 structure of the Osmoregulatory Leaf Cells," American Journal of Botony, 

 Vol. 60, No. 10, Oct. 1973, pp. 1003-1009. 



Turtlegrass (Thalassia testudinum) grows completely submerged and differs 

 from intertidal and other halophytic angiosperms in that it has no specialized 

 salt-secretory glands. Osmoregulation appears to be by the epidermal leaf 

 cells. The ultrastructure and proposed mode of secretion are similar to that 

 of the salt marsh monocot, Spartina, but differ from that found in dicots. 



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