monochrome texture

I used glTexImage2D to zoom and scroll grayscale images, and works great. I would like to do the same with monochrome images. But when I changed the format parameter from gl_unsigned_byte to gl_bitmap I had a blank screen. If I use gl_unsigned_byte with a monochrome data source, it seems to work, but the quality is very poor. Anyone knows the best way to display monochrome textures? I mean, directly from OpenGL, not by first converting them to grayscale.