The next tree is known to most people as Australian pine. It is not a true pine, but rather a flowering plant. In true pines the needle is the leaf. In Australian pine what appears to be a needle is actually a stem, and the leaves are about 1 mm long in small whorls at joints along the length of the needle-like stem. 

The number of these small leaves per whorl, and the presence or absence of a brown band in the leaves is part of how the various species are distinguished. The leaves are visible in the picture below.

There are three species of Australian pine in Florida, and two of these are found in the Thousand Islands, along with a third type that is thought to be a hybrid. 

Below are the male flowers of Casuarina glauca. Male and female flowers are found on separate trees in this species, and there are no female trees in North America. This tree reproduces by sending out long root suckers, and new trees sprout from the root, as seen in the following slide. 

It also appears to be able to reproduce by fragmentation; even a small needle-like branch can sprout of it is blown off a parent plant and it lands in the soil under the right conditions. 

Below is another species, Casuarina equisetifolia, as can be seen in the next slide, the male flowers and the female fruits, which look like cones, are both found on the same tree. This tree reproduces by seed and does not sucker. 

And following is a close up of the cones and then the small seeds which are only about 1.5 mm wide.

This is a third kind found in the islands, thought to be a hybrid between the two previous types. It shows suckering and has both male and female flowers on the same tree. It is also thought to show greater tolerance of cold. 

Continued Here