S. Cyril here, and still more emphatically in xiii. 39, distinguishes the hyssop (John xix. 29) from the reed (Matt. xxvii. 48), implying that the sponge filled with vinegar was bound round with hyssop, and then fixed on a reed.  Another opinion is that the reed itself was that of hyssop.  See Dictionary of the Bible, “Hyssop.”