Art glass vases - origin?

Apologies for the lopsided image, but I believe these vases travelled from England to Australia in the early part of last century, when my maternal grandmother and great-grandmother migrated. They are appox 30cm tall and although I am not sure of the production method, it appears a layer of clear glass and black trails was moulded over an inner orange/tango (?) shell. There are no discernible markings on the base, but it has a slightly 'nobbly' surface, possibly from a mold? Would be interested in any thoughts re origin. I have always known them in our house, but not their story. Thanks.