Botanical Ecology of the Dry Tortugas. 121 



The booby, a kind of gannet, is said to have inhabited these islands, 

 but has disappeared with the passing of the trees. Old fishermen 

 relate that men, armed with clubs, would stealthily creep into the 

 groves of buttonwood at night and kill perhaps hundreds of these 

 birds out of pure wantonness, as they had little or no economic value. 

 The same wanton spirit which eradicated the Conocarpus groves and 

 the " boobies" in these islands has been shown by the people of the 

 region in regard to the manatee, which is now nearly extinct in these 

 waters; the large green and loggerhead tortoises are also fast disappear- 

 ing, due to a custom of eating the eggs and killing the females. During 

 the breeding-season of 1916 not over 6 females were reported in these 

 islands as coming in to lay, and two of these were killed after laying and 

 the entire settings of eggs taken, whereas even ten years ago it is said 

 that as many as a dozen females came up on the beach in one night to 

 lay on Loggerhead Key. 



The vegetation of Loggerhead is remarkably free from the common 

 tropical weeds when compared, for example, with Garden Key. This 

 is probably because this island has never, since its first permanent 

 occupation 75 years ago, been brought into frequent contact with the 

 mainland by ships, men, or animals, except for a few months shortly 

 after the Civil War, when a quarantine camp was established for the 

 marines brought over from Fort Jefferson during an epidemic of yellow 

 fever. The only permanent residents now are the keepers of the light- 

 house ; while the monthly call from Key West of the cutter of the Light- 

 House Establishment, which rarely lasts over 2 hours at Loggerhead 

 Key, does not seem to have served for the introduction of homovectant 

 plants. 



A glance at the distributional map of Loggerhead will show that two 

 of the four associations mentioned above are represented in the island, 

 the Suriana community predominating and the Opuntia association 

 supplementing it. A photograph taken from the top of the light-house 

 shows the vegetation to be distributed in sharply defined areas follow- 

 ing irregular outlines. It is supposed that some of the central areas 

 now occupied by the Opuntia formation (see plate 3) was cleared of 

 the dense growth of Suriana by the marines and soldiers who camped 

 there during the epidemic of yellow fever mentioned above, but the 

 irregular outline and the isolated patches of Opuntia among the Suriana 

 show that other agencies than man have helped to clear portions of the 

 island. 



As remarked before, the Suriana does not withstand a drenching of 

 sea-water very successfully, the tomentum of the leaves holding the 

 water until its toxic effect is produced on the leaf-tissue. The great 

 hurricanes of the past must undoubtedly have had their share in cutting 

 out some of the swathes in the Suriana community. In the list of 

 species and on the map also some large introduced plants appear, 



