128 Papers from the Department of Marine Biology. 



tree, which produces fruit quite abundantly, as do also the date palms 

 and tamarind. The parade-ground is carpeted with many small 

 native weeds, as Boerhaavia, Bidens, Ipomcea, etc., as well as introduced 

 ones, Portulaca, Argemone, Lepidium, Ricinus, Dolicholus parwflorus, 

 Cajan cajan, Sida procumbens and S. carpinifolm, Phyla nodiflora, 

 Sonchus, Leptilon, etc. 



On the earth-covered ramparts built on the top of the casemates a 

 number of plants have secured an elevated and very dry footing. 

 These are Opuntia, Melanthera, Canavalia, Valerianoides, Sporobolus, 

 ChamoBsyce, Paspalum, and Bidens, and in shielded crevices several 

 good-sized trees of Elaphrium simaruba have managed to thrive 

 (see plates 4 and 6). 



The species listed on this interesting old key are 35, the number that 

 Lansing and Millspaugh give for the same area i. e., for the portions 

 outside of the fort; the parade-ground is omitted as having been 

 too much under artificial influence to be of much importance in an 

 ecological study; but these 35 species are not identical, for 9 of the 

 Lansing species were not obtained in this area by the author, viz, 

 Amaranthus nridis, Cenchrus echinatus, Euphorbia Jiavanensis and E. 

 adenoptera, Eustachys petrcea, Heliotropum curassavicum , Sida carpini- 

 folia and S. diffusa, and Capraria saxifragifolia, although the last 

 three or closely related species were found inside the fort. The 9 new 

 species introduced into the given area are Lepidium, Guilandina, 

 Ricinus, Chamcesyce hypericifolia, Thespesia, Rhizophora, Calonyction, 

 Avicennia, and Leptilon. In cases of doubt concerning species, e. g., 

 Sida diffusa of Millspaugh and Sida procumbens S. Watson, as men- 

 tioned in this paper, the synonymy could not be exactly traced, since 

 Millspaugh did not give the authors of his species. 



BUSH AND LONG KEYS. 



The general map of the Tortugas shows that these keys lie slightly 

 west of Garden Key; they are very irregular and are merely narrow 

 strips of sand and ridges of broken corals. During the winter season of 

 1911-12 the two keys were united by land connections due to storms, so 

 that the outline is now that shown in the distributional map given here. 

 The western end seems to have been the longest elevated out of the sea 

 and supports the most vegetation. The eastern end, however, has tc 

 bear the brunt of the storms and the waves driven in by the prevailing 

 winds, and it is perhaps for this reason that the vegetation is more scant. 



Lansing and Millspaugh omitted treating this key as being "so low 

 as to be awash during heavy weather and on this account void of vege- 

 tation." If these conditions obtained then the keys must have been 

 built up within a year or two after Lansing's survey, since stem meas- 

 urements on some of the Suriana and Tournefortia bushes on this key 

 show them to be almost 12 years old by comparison with plants of the 



