Вот что пишет Фергюссон:

The gourd is prominent in the story of Jonah, and, because of this association with him, has become to symbolize the Resurrection (Jonah 4). When painted together with an apploe, the gourde, as the symbol of the Resurrection, is the antidote for the apple, the symbol of evil, or death.

The gourd was used by piligrims as a flask to carry water. It is the special attribute of St. James the Great, and of the Archangel Raphael and is sometimes given to Christ, who, dressed as a piligrim, joined the two Apostles on their way to Emmaus. Frequently, in art the gourd resembles a cucumber.

Now I see where Met's redemption theory comes from: botanical confusion. Why would Crivelli paint a gourd that looks exactly like a cucumber, time and time again? Crivelli knew very well how a gourd looks like; it is not an exotic fruit. What Fergusson writes about gourds is absolutely correct, but cucumbers "representing" gourds is odd.One may as well suggest that cucumbers represent carrots.

Cucumbers do have reach symbolism of their own, albeit less settled. In this particular painting cucumber might stand for lust (which is one of these symbols). Then one has the complete set around Maddona and baby Jesus: lust (cucumber), sin (apple), evil (fly), death (crack). The whole unholy gamut of the Original Sin.

Заранее оговорюсь, что мои поздания в ботанике минимальны. Мудрый Гугль подсказал, что и огурец, и горлянка (она же тыква посудная) принадлежат к одной и той же группе Cucurbitaceae (Тыквенные) - может быть они похожи друг на друга? Мне очень хочется верить в Ваше объяснение, или хотя бы в греховность огурца, но откуда-то же взялась идея отождествления огурца с горлянкой?!