evolution, and geographical distribution of seagrasses are also discussed, and 

 a key to the Identification of sterile specimens is included. 



45. HARTOG, CD., "Structure, Function, and Classification in Seagrass Com- 

 munities," Seagvass Eaosystem: A Saientifia Pevspeative, C.P. McRoy and 

 C. Helfferich, eds.. Marcel Dekker, Inc., New York, 1977, pp. 89-121. 



The seagrasses are divided into six growth forms. These growth forms are 

 linked to differences in ecology. It is suggested that the ability of the 

 plant to compete is linked to growth form. The complexity and functions of 

 community structures of seagrasses are described. 



46. HECK, K.L., Jr., "Comparative Species Richness, Composition, and Abundance 

 of Invertebrates in Caribbean Seagrass iThatassia testudinum) Meadows 

 (Panama)," Marine Biology, Vol. 41, No. 4, 1977, pp. 335-348. 



This article reports on a year-long study of epibenthic invertebrates from 

 seagrass (Thatassia testudinum) meadows along the Caribbean coast of Panama 

 and the Panama Canal Zone. Differences in species composition and abundance 

 among sites were primarily due to the proximity of surrounding habitats. Coral 

 reefs contained many species that utilize the seagrass meadows. Important sea- 

 sonal fluctuations in both species number and abundance occurred at each of 

 the sites. Several species of decapod crustaceans bred year round although 

 seasonal differences occurred in the percentage of oviparous females. Overall 

 species composition was similar to that reported in tropical and subtropical 

 seagrass meadows elsewhere. 



47. HILLSON, C.J., Seaweeds: A Color-Coded, Illustrated Guide to Common 

 Marine Plants of the East Coast of the United States, Keystone Books, 

 Pennsylvania State University Press, University Park, Pa., 1977. 



This is a color-coded guide to the identification of marine plants, in- 

 cluding turtlegrass (Thalassia testudinum) and eelgrass (Zostera marina), 

 commonly found on the east coast of the United States. A glossary and a bib- 

 liography are also included. 



48. HIRTH, H.F., KLIKOFF, L.G. , and HARPER, K.T. , "Sea Grasses at Khor Umaira, 

 People's Democratic Republic of Yemen, with Reference to their Role in the 

 Diet of the Green Turtle, Chelonia mydas," Fisheries Bulletin, Vol. 71, 

 No. 4, Department of Commerce, National Marine Fisheries Service, Oct. 

 1973, pp. 1093-1097. 



Studies were made on the seagrass pastures at Khor Umaira, the People's 

 Democratic Republic of Yemen, in July 1972. The standing crop in an equally 

 mixed pasture of Cymodoaea serrulata and Syringodium isoetifolium was greater 

 than in a pure stand of C. serrulata. The average caloric content of the 

 leaves of five genera of seagrasses at Khor Umaira ranged between 4.54 and 

 4.66 kilocalories per gram dry weight, ash-free. These values are similar to 

 the values reported for seagrasses in the South Pacific and in the Carib- 

 bean. The results show that the number of calories in the standing crop can 

 be calculated from estimation of percent cover. The role of seagrasses in the 

 management schemes of the green turtle {Chelonia mydas) is described. 



49. HOTCHKISS, N. , Common Marsh, Underwater and Floating-Leaved Plants of the 

 United States and Canada., Dover Publications, Inc., New York, 1972. 



This is a reprint of two circulars on field identification of marsh and 

 water plants in North America. It describes all of the wild-flowering plants, 

 ferns, liverworts, and Characeae which have underwater or floating-leaved 



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