Meaning of "barrer" (noun) in W. Henley's poem "'Liza"

Eric Partridge, A Dictionary of Slang and Unconventional English, fifth edition (1961), may be citing this very passage in his entry for pearlies:

pearlies. (The singular hardly exists.) Pearl buttons, esp. on a coster's clothes : from ca. 1885 : low coll. Henley.

A coster or costermonger, Partridge says, is "orig. costard-monger, at first a seller of apples, then of any fruit, finally of fruit, fish, vegetables, etc.., from a barrow," which clarifies the "barrer" part of the line.

Unfortunately, jack has so many slang meanings—including, Partridge says, "A single carnation (sold as a choice carnation) : horticultural s[lang] (—1878)" and "A variety of tea-rose : coll. : abbr. Jacqueminot : 1883"—that I have no idea which one Henley intended here. The carnation would go with the mother-of-pearl buttons, you might think, but there are numerous other possibilities.

As for "all the vegetables of the year" being represented on Liza's back, perhaps she wears the seasonal leftovers from the barrow on her hats each day, thereby justifying the simile "like a load of bricks."