Older constitutions often vest this power in the cabinet. In the United Kingdom, for example, the tradition whereby it is the prime minister who requests a dissolution of parliament dates back to 1918. Prior to then, it was the entire government that made the request. Similarly, though the modern 1937 Irish constitution grants to the Taoiseach the right to make the request, the earlier 1922 Irish Free State Constitution vested the power in the Executive Council (the then name for the Irish cabinet).
Try to answer this question if possible (otherwise reply "unanswerable"): In Ireland, when was the power to dissolve parliament assigned to the prime minister?
1937