when your texture is using the alpha channel (32 Bit png or tga) you can use the alpha flag to load it. When you wish to load the model without to load the texture manually, I'd suggest to:
Cleartexturefilters
Texturefilter "",9 or 2
m=loadmesh("tree.x")
texturefilter "",9
Tho this will use the alpha flag for all textures that are used by the mesh.
For Leaf you maybe rather should use the Mask mode (flag 4 instead of 2). Masked areas have to be black in the rgb channel.
Cleartexturefilters
Texturefilter "",9 or 2
m=loadmesh("tree.x")
texturefilter "",9
Tho this will use the alpha flag for all textures that are used by the mesh.
For Leaf you maybe rather should use the Mask mode (flag 4 instead of 2). Masked areas have to be black in the rgb channel.