"But what is most curious is the number of absolutely dissimilar senses which the oldest symbolists attribute to the buckthorn.

Saint Methodus uses it for virginity; Theodoret for sin; Saint Jerome ascribes it to the devil; and Saint Bernard takes it as symbolizing humility.

Again, in the '_Theologia Symbolica_' of Maximilian Sandaeus, this shrub is made to signify the worldly prelacy, while the olive, vine, and fig, with which the author contrasts it, are the contemplative Orders.

In this, no doubt, we may see an allusion to the thorns which Bishops were not always unready to thrust on the long-suffering Heads of monasteries.
"You have forgotten, too, in the blazonry of your chapel, the reed which formed the sceptre of mockery forced into the Son's hands.

But the reed, like the buckthorn, is a sort of Jack-of-all-trades.