the origin of the ambrosian rite is still under discussion, and at least two conflicting theories are held by leading liturgiologists. the decision is not made easier by the absence of any direct evidence as to the nature of the rite before about the ninth century. there are, it is true, allusions to various services of the milanese church in the writings of st. augustine and st. ambrose, and in the anonymous treatise "de sacramentis", which used to be attributed to the latter, but is not his; but these allusions are naturally enough insufficient for more than vague conjecture, and have been used with perhaps equal justification in support of either side of the controversy. even if the rather improbable story of landulf is not to be believed, the existing manuscripts, which only take us back at the earliest to the period of charlemagne, leave the question of his influence open.