Kitniyot - Ashkenazic perspective - Igrot Moshe Orach Chaim 3:63

In this teshuva from 1966, Rav Moshe deals specifically with whether or not peanuts fall under the rubric of kitniyot. In answering the question, he attempts to define the parameters of the prohibition. He cites the various rationales offered by earlier commentators and decisors, including the ideas that kitniyot can also be made into flour like grain, that they are planted in the fields in a manner similar to grain, and that perhaps some grain was mixed in with the kitniyot (and would result in chametz without the person realizing it). While Rav Moshe favors the latter reasons, he says that since the decree of kitniyot was not made with a full Rabbinic council, therefore the decree is limited to the species that were originally included in it. As such, he feels that the decree of kitniyot should remain a limited one, and peanuts should not fall under it. However, he does note that there are those who do include it as kitniyot and they should stick to their view. [My note - this view of kitniyot seems to run counter to the view currently held by some that kitniyot can be expanded to include new species. It is also a maddening teshuva for a peanut lover to read, since Rav Moshe seems to allow peanuts on Pesach, and yet it is fairly accepted by now that they are kitniyot.]