A Scribal and Illuminated Rebus?

Among the digitized manuscripts at Villanova University, PA, is a very small (approx.100×70mm) 14th-century English copy of some of Augustine's works, with a single illuminated page at the beginning:

[This and other images: Digital Library@Villanova University; Source]

The thing that strikes me as most unusual about this first page is the lower border, with foliage sprouting from what looks like a hole in the side of a wooden barrel:

John Batayle and the Smithfield Decretals

The Smithfield Decretals (British Library, Royal MS. 10 E.iv) is an exceptionally large (c.450 x 285mm.) and lavish (including more than 600 narrative bas-de-page scenes) copy of the Decretals of Gregory IX with the gloss of Bernard of Parma, thought to have been written in southern France c.1300, with decoration and an extra prefatory quire added in England some decades later.

The BL website has an online description with partial digitization and a description with full digitization.

Source

The main reason I found fault with a recent monograph on the Taymouth Hours is that it tends to treat hypotheses as facts. One of several such hypotheses is the proposal that the Smithfield Decretals was made for man called John Batayle who was a canon of St Bartolomew's, Smithfield, in the last quarter of the 14th century. This may be true, or it may not.