Can you use masked textures for leaves in Blitz3d?
Sure... I use 32-bit .TGAs (that have alpha channel) and it works just great.
http://www.blitzbasic.co.nz/b3ddocs/command.php?name=LoadTexture&ref=3d_a-z
2: Alpha - alpha map. If an image contains an alpha map, this will be used to make certain areas of the texture transparent. Otherwise, the colour map will be used as an alpha map. With alpha maps, the dark areas always equal high-transparency, light areas equal low-transparency.