According to Montesquieu in The Spirit of the Laws, who should exercise executive and legislative powers?

Montesquieu argued for a mixed, or moderate government in which the excesses of the three types of government--government by the people, by the aristocracy, and by a monarch--might be moderated. Putting it as simply as possible (The Spirit of the Laws is a very complex book, with many contradictions) Montesquieu generally thought that legislative branch ought to reflect the will of the people, and be controlled by their representatives. He deeply admired the English "mixed" constitution, under which Parliament also included nobility in the House of Lords, but the important thing was that the body represented the will of the people, particularly property owners. As for the executive, Montesquieu generally understood executive power as exercised by a monarch. Again, he deeply admired the British constitution, in which the king held powers that were limited in practice by his council and by Parliament. The crucial point for Montesquieu was that a mixed government would restrain the abuses that could occur under different types of "pure" government--democracy, aristocracy, and despotic monarchies.