The interior of the fort has a large parade-ground (plate 4) and vari ous buildings and ruins. This parade-ground has been planted with some introduced trees, as mentioned by Millspaugh, but a curious omission in that survey was the grove of large and old white button wood trees just within the sally-port. This grove is quite large and thick, and numerous young seedlings have sprung up among the older trees. While the fort was a military fortress, then during its period of use as a federal prison, later as a quarantine station and coaling-depot, and now under the jurisdiction of the naval authorities, up to date the order has been handed along that these old trees (the only remnant of the traditional forest or thickets which covered these islands) shall be untouched (see plate 4) .
Notwithstanding the tendency and inclination of various care-takers of the fort to cut down and destroy all plants springing up inside the fort and the practice of burning over the parade-ground at regular intervals, and the serious fires in the fort which destroyed the large barracks and the keeper's cottage, these old trees have persisted to the present and are now strong and healthy. An interesting sport was noted in the grove, viz, a few young plants of Conocarpus erectus var. sericius. This variety probably arose quite recently as a genetical variation, very likely a mutation, as these gray tomentose trees are all quite young and have started as seedlings right in the midst of the old trees, which all have dark-green and glabrous foliage. The center of the old parade-ground is occupied every year by a thick stand of the weed Glottidium vescarium, which the care-taker tries to destroy by burning over the ground annually, but to no avail.
Agave decipiens (see plate 6) and in a ruined powder magazine there has sprung up, with a thicket of gum-elemi trees, a fair-sized guava 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, Ipomoea, etc., as well as introduced ones, Portulaca, Argemone, Lepidium, Ricinus, Dolioholus parviflorus, Cajan cajan, Sida procumbens and S. carpinifolia, 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 0-puntia, Melanthera, Canavalia, Valerianoides, Sporobolus, Chamceayce, 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 Cenchrus echinatus, Euphorbia havanensis and E. adenoptera, Eustachys petrcea, Heliotropum curassavicum, Sida carpini folio 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.