To create a tree within Bryce 5 is easy. Whatever tool you use, I recommend using not black as the background. Try to use the approximate colour of the environment where the tree is going to be settled. That's mostly a green environment.

First click with the magic wand (keyboard "W") in the green background. The settings at the left side cause: tolerance 1 = only this colout will be selected, smoothing on = where the selected the colour meets other colours the selection will be smoothed. Then there will be a new colour mixed of the two bordering colours, neighbouring off= select the colour in the whole picture. That means also in between the branches.

Now invert the selection (shift + strg + I). You've selected the tree completely and deselected the background. Now you have to increase the brightness at 10. By using this method we give the black spots in the tree (for example knotholes) a colour value which is in any case higher than RGB = 0. With this we ensure that there will be no holes in the trunk later.

Copy now the tree which is still selected. Then create a new bitmap with black background. Photoshop will adapt the size automatically to the copied part of the image. Now paste the tree into the picture and save it in the PCX file format. In the image we can see the green border slightly, in the game environment wo won't notice it.