Flora of Eniwetok Atoll' HAROLD ST. JOHN2 EN1WETOK ATOLL is near the north end of the summary of the flora of Eniwetok. They are now Marshall Islands which form the northeastern in the Bernice P. Bishop Museum, Honolulu. part of Micronesia, in the tropical, central Paci­ In mid-May, 1946, the ship of the Economic fic Ocean. The Marshall Islands were discovered Survey of Micronesia, U. S. Commercial Corpo­ in 1817 on the "Rurik" voyage under Captain ration, tarried in the Eniwetok lagoon. Large Otto von Kotzebue. A member of the scientific botanical collections were made for it by F. staff of this voyage was the German botanist, Raymond Fosberg and a small collection by Adelbert von Chamisso. He made extensive Edward Y. Hosaka. These collections are pre­ plant collections in the Marshalls and included served in the U. S. National Herbarium, Wash­ them in his publications on the voyage. Though ington, D.C., and in the Bishop Museum. this voyage of discovery included landings on Broad scientific studies began in the area in several of the atolls, Eniwetok itself was not connection with the American atomic bomb visited. testing program. The first test shot was at There are no accounts of the flora of Eniwe­ Bikini Atoll in 1946. Connected with this were tok during the successive occupations of Micro­ the investigations accomplished by the Cross­ nesia by the Spanish, or by the Germans. Next roads Expedition. On its staff was William Ran­ in the succession of rulers were the Japanese. dolph Taylor. In late May, 1946, he made collec­ Their scientists made wide explorations of tions on several of the islets of Eniwetok. They Micronesia, and particularly through the work are preserved in the U. S. National Herbarium, of R. Kanehira and T. Hosokawa added much the University of Michigan Museum, and the to the knowledge of the Micronesian flora. In Bishop Museum. The plants of Eniwetok were August, 1934, Ohba made collections of several included in Taylor's book, Plants of Bikini, and species of Pandanus, these being apparently the Other Northern Marshall Islands, 1950. first botanical collections from Eniwetok Atoll. During August, 1949, the ship of the 1. R. They were studied, and published upon, by Donaldson Expedition, U. S. Atomic Energy Kanehira, and are preserved in the herbarium Commission, was the base for investigations of at Fukuoka, Japan. the lagoon and the islets. The writer, H. St. In World War II, during the American con­ John, was the botanist and ecologist for the quest, in February, 1944, there was heavy bom­ terrestrial flora. His numerous collections are in bardment and fighting on Eniwetok. This caused the Bishop Museum, the Smithsonian Institu­ general devastation on the largest islet, Eniwe­ tion, Washington, D.C.,the University of Wash­ tok Islet, and on several others . It probably ington, Seattle, and elsewhere. exterminated some of the rarer plant species. On August 1, 1956, S. C. Rainey collected on During the occupation of Eniwetok by the Rigili. His specimens were identified by F. R. American military forces, Major Edwin H. Fosberg in Washington, D.C. Bryan, Jr., visited the atoll in August, 1944. He collected plant specimens and made additional In August and September, 1957, Irwin E. notes on the flora. These gave the first general Lane collected on several of the islets. His speci­ mens are in the Bishop Museum. 1 This report has been submitted to and cleared for In early August, 1958, St. John collected on publication by the U. S. Atomic Energy Commission. several of the southern islets of the atoll. His 2 Visiting Professor of Botany, Chatham College, Pittsburgh, Pennsylvania. Manuscript received June collections are in the Bishop Museum, and the 20,1959. Marine Biological Laboratory, Eniwetok. 313 3 14 PACIFIC SCIENCE, Vol. XIV, October 1960 LOCATI ON AND TOPOGRAP HY the Marshalls and the central Pacific. The two species of south ern or western origi n may have Eniwetok Atoll is found near the northern travelled eastward on the Equato rial Counter end of the double chain of atolls forming the 0 Current and have been wafted northward dur ­ Marshall Islands. It is at 11 0 30' N. , 162 14' E. ing a southe rly storm. Its shape is a broad ellipse, running NW to SE. Its length is 22 nautical mi. The reef is well developed and nearly continuous, but with sev­ ECOLOGY eral deep passages from the sea to the lagoon. Details of .the terrestrial plant ecology were The islets total 39, and nearly all of them and reported to the Atomic Energy Commissio n in all the large ones lie on the northeastern or 1950. They were for publication in UWFL-24. windward side. The largest islets are Eniwetok, Parry, Engebi, and Runit. Eniwetok, the largest, Because of the dryness and the small, mostly is 2 ~ nautical mi. in length. narrow, islets, there is little diversity in the habita ts. There are no good sand dunes, or fresh SIZ E OF THE FLORA ponds, or central hollows with rich, black humus top soil. Th e only habitats are: outer beaches of Eniwerok is in the nort hern and drier section coral rock or coral gravel, inner beaches of coral of the Marshall Islands. As a consequence it sand, small coral sand dunes, coral gravel flats, does not have, and probably never had, dense, and coral sand flats. Some of the plants seem lush, damp forests, nor is its total flora large. restricted to a particular habita t, but the zones Its indigenous flora totals 42 species or minor formed are rather indefinite. Their occurrence taxa, of which 4 are endemic, all of these four seems governed not so much by the soil, as by being in the genus Pandanes. The total of ad­ the size of the islet and the distance from the ventive weeds is 27, and that of cultivated sea which seems to determine the shelter from plants, including both food crops and ornamen­ salt spray, and the availability of fresh water tals is 26. Species known only by drifted seeds in the water table. Since the habitat differences -on the beaches total 7. All together the living are slight, they have, for the sake of brevi ty, Bora totals 95 species or mino r taxa. been omitted in the descrip tive flora which fol­ Seeds or fruits found in the jetsam on the sea lows, except when special and very local. In and lagoon beaches add an element in the flora. this flora every known collection is briefly cited Many come from species growing on the islets with its islet, date of collection, and collector's of the atoll, but there are others from species name and the number. From this, future re­ unknown on the island and certainly floated on the sea currents or waves from distant regions. search workers can learn the former occurrence Of these H ernandia sonora is the only one that of each species, and the date for each record. is native to other islands of the Marshall group, This chrono logical information is of value, since ones to the south in the wetter belt. Two spe­ it appears that each atomic bomb explosion has cies, Caesalpinia Bonduc and Aleurites moluc­ restr icted, or may restrict, the occurrence of, or cana, are of wide occurrence and could have exterminate some members of, the flora. come from the northeast, south, or west. These are both abundant in Hawaii. Two species, ACKNOWLEDGMENTS MUCUl1a urens and Sapil1dus Sapol1aria, must have come from the northeast, being abundant The author's sincere thanks are due Dr. in Hawaii and absent in other parts of the tropi­ Lauren R. Donaldson of the Radiation Biological cal Pacific. Two species, Dioclea reflexa and Laboratory, University of Washington, Seattle Entad« pbaseoloides, must have come from the 5, Washingto n, and Dr. Leonard D. Tuthill, south or west. In sum, of the 6 drift species, 4 then dean of the Graduate School, University of certainly floated from Hawaii on the Japan Cur­ Hawaii, Honolulu 14, Hawaii, for making pos­ rent which regularly flows past Hawaii towards sible the writer's two explorations of Eniwetok. Flora of Eniwetok-ST. JOHN 315 PURPOSE types of research are being carried on now on This account of the flora of Eniwetok is pre­ the atoll. The investigators have diverse training pared in the form of a brief manual. It sum­ and come from widely separated institutes. marizes the flora, and it gives keys and brief When their researches touch the terrestrial flora descriptions to make possible the identification this manual will enable them to determine with in the field of any of its plant species. Many certainty the identity of the plants. KEY TO SPECIES PTERIDOPHYTA 1. Plants lacking flowers, reproducing byspores; frond pinnately lobed __1. Phymatodes Scolopendria 1. Plants with flowers, repr oducing by seeds, SPERMATOPHYTA 2. Flower parts in 3's; leaves parallel veined; herbs, and trees but these without secondary wood, 3. Trees, MONOCOTYLEDONES 4. Fruits aggregate into heads 15 em. or more in length, 5. Carpel apices concave, 6. Phalanges 7.5-8 em. long, 7.Inner apical sinuses 2-3 mm . deep ; syncarps globose__ 2. Pandanus brachypodus 7.Inner apical sinuses 1-2 mm. deep; syncarps ellipsoid ... 3. P. enchabiensis 6.Phalanges 6.5 em. long; sinuses 2- 3 mm . deep 8. P. rectangulatus 5. Carpel apices all, or at least the inner ones, convex or conical, 8. Phalanges 7-9 em. long, 9. Inner apical sinuses 1-2 mm. deep; outer carpels much the larger...._...__. _ .__..._.._....._._ .