Take a quick boat ride from Robbie's Marina in Lower Matecumbe across the Indian Key Channel and step back in time onto Lignumvitae Key. A perfect two-hour jaunt for history buffs and nature lovers alike, the island is home to the 1919 Matheson house and one of the few remaining tropical hardwood hammocks in the Keys.</p><p>"It's more or less in its native state," said Keys historian Jerry Wilkinson. "We could imagine that going onto Lignumvitae Key today — other than the house and the small grove of coconut trees — it would be as if you were going onto the island 500 years ago. It's one of the few places that humans have had little impact."</p><p>Any written history about the island doesn't begin until the 1800s, when early Keys settlers began using the island for farming. Also, according to Wilkinson, the island was used during the Spanish American War in 1898 as a place to store coal for ships. </p><p>The island traded hands several times in the 1800s, and it was finally purchased in 1919 by William J. Matheson, a wealthy American chemist, who also had an estate in Coconut Grove and a coconut plantation on the northern two-thirds of Key Biscayne. Matheson spent the latter part of his life traveling and studying tropical plants, discerning their commercial importance. </p><p>The Matheson family owned the island until 1953, when they sold it to developers who wanted to turn it into a resort. They drew up plans to build a causeway onto the island, but public protests put their ideas on hold. </p><p>"That would have caused irreparable damage," Rose said. "It was also going to close off Lignumvitae Channel and alter a premier bonefishing flat. That's when the battle ensued and lawsuits flew."</p><p>Using funds set aside by the state's Land Acquisition and Trust Fund, the Nature Conservancy purchased the island in 1970 and turned it over to the state. It was added to the National Register of Historic Places in 1999.</p><p><b> Home in good shape</b></p><p>When Matheson bought the island, he built a home for his caretaker, which is still in good condition today. Other than when the devastating 1935 hurricane tore off the roof, windows and doors, the building has survived the tumultuous South Florida weather relatively intact. "It's built from mortared limestone rocks and imported Dade county pine, and this combination makes for a very strong structure," Rose said. "This is a very hard dense pine. It can easily be two to three times as heavy as normal pine."</p><p>Attached to the house is the concrete cistern, which was the only source of water at that time, and it is still used today for watering the grounds. Also, in front of the house are four cannons, which were recovered from the British warship HMS Winchester. The ship ran aground on Carysfort Reef in 1665.</p><p>Aside from the house, there are several other structures that are of mysterious origin. There are remnants of a stone wall and chimney near the edge of the forest on the front lawn, but no one knows when the structure was built and by whom. There's also a 3,000-foot coral rock wall on the west end of the island that stands about 4 feet tall and about 3 feet wide, which is typical of Bahamian construction. "We think it could have been used for livestock," Wilkinson said.</p><p>Lignumvitae Key's true treasure is its 280 acres of tropical hardwood hammock, which is home to roughly 50 plants and trees, many of which are endangered. </p><p>"Lignumvitae is one of the finest examples of West Indian tropical hardwood hammock that we have in the U.S.," Rose said. "Its 16 1/2 feet of elevation is a critical factor in the Keys since the average elevation is only 6 1/2 feet. You have to travel out of the country to see the same thing, but that's a pretty pricey trip. You can come to Lignumvitae and see it right here in the U.S. in living color."</p><p>The lignumvitae tree, for which the island was named, is listed as an endangered species by the state of Florida. It was once common on the lower Florida Keys and Key West, but it was almost completely exterminated by overharvesting for its wood, which is the hardest of any commercially harvested tree. "It has a very tight dense grain," Rose explained. "The actual grain of the tree grows in a slow spiral around the branch. The following year, the spiral will go in the opposite direction. It creates a strong wood that is knitted together by these layers."</p><p>More significant than its strength is the high resin content of the Lignumvitae tree, which is about 30 percent by weight and makes the wood very oily. Wilkinson explained that the wood was of particular use during World War II in the propeller shafts of submarines. "They needed a self-lubricating bearing for turning shafts that didn't turn real fast and didn't make noise, so that sonar wouldn't detect them," he said.</p><p>Also known as the tree of life, the tree's oil was once thought to have healing properties. "It was a product that was kept warm in a liquid state and was consumed, assuming it was curing you of some problem like syphilis or arthritis," Rose said.</p><p>Lignumvitae grows slowly, and the island has several trees that are as old as 500 to 1,000 years that have grown up to 25 feet tall. It sprouts blue flowers between March and April, and it produces a brown fruit that ripens in September to October to expose black seeds that are enclosed in a red pulp. </p><p>Rose noted that some of the other more interesting trees growing on the key include varieties of ficus, which can grow to cover half an acre of land and 60 to 80 feet tall. "Everybody gets sort of a Tarzan kind of feel around this tree because it has these long dangling aerial root systems that hang down from the branches. When the roots make contact with the ground, they begin to thicken and become a stand to allow the branch to extend farther again."</p><p>One of the challenges facing Lignumvitae Key is the invasion of the non-native plants and trees, which tend to lose their control factors when they are out of their natural environment. Part of the park's mandate is to control and eliminate all exotic plants from the island. "Usually there's a plant, animal or weather condition that keeps plants from going helter skelter," Rose said. "Without that, they can take over, ruining the habitat. It's something that we work against 24/7. We spend a great deal of money doing it."</p><p>Raccoons, bush rabbits, rats and many species of birds call Lignumvitae Key home. In front of the house is a tall bird tower where osprey have nested and hatched babies. Year-round the island is host to wading birds such as great white herons, American egrets, little grey herons and great blues. Rose explained that seasonally, the island sees a lot of migratory activity. "We're on the tail end of the eastern flyway that runs from Nova Scotia to the Yucatan peninsula. You name it; if it lives on the Eastern seaboard, then it probably comes by here."</p><p>The flowering plants on Lignumvitae make it an ideal stop for butterflies as well. They come mostly in springtime with the warmer weather, but many of the species can be seen year-round. "The Florida skipper is a common one that we see most of the time," said Rose. "Most places you can only see them in springtime. We also get the Florida purple wing, yellow and orange sulphers, Florida whites, southern whites, checkered whites and swallowtails."</p><p>The park has a maximum occupancy of 50 people, and no more than 25 people at a time can be on a tour. No one is allowed into the hammock unescorted. Park rangers meet visitors at the house and give a 15- to 20-minute tour of the house and the grounds, showing visitors how the house was constructed. They talk about the history of Matheson himself and the caretakers who lived on the island. Then they take visitors back into the hammock and talk in detail about the plants and wildlife.