Saying ascribed to Montaigne

The saying, "I have here only made a nosegay of culled flowers, and have brought nothing of my own but the thread that ties them," is usually ascribed to Montaigne. In what part of his works are these words to be found? I heard doubts expressed of their genuineness some years ago by a reader of the *Essays*; and my own search for them has also proved hitherto unsuccessful.