Wheat that came from an Ancient Egyptian
tomb. In the nineteenth century it was widely believed that this could grow again if sown. Botanist
s always insisted it was impossible, but the story persisted.
It is definitely not true, but then again it's not a self-evidently silly idea either. After all, if it's actually inside the mummy, within or attached to the bandages, it could be preserved in much the same way many of the human tissues were; and if it's outside, in the sarcophagus or in corners of the tomb, it's still been resting in a very stable, temperature-controlled environment.
Egyptology took off with Napoleon's expedition to the Nile in the late 1700s, and later the decipherment of the Rosetta Stone and thence of the whole language. Tourists and collectors brought back all sorts of Egyptian artefacts. No doubt the mummies had an especially gothic fascination, and it was natural to apply the idea of bringing the dead back to life to the grain that came with the corpses and sarcophagi.
There was also a biblical antecedent: Pharaoh's dream that he related to Joseph, with seven ears on one stalk of corn being interpreted as seven years of bumper harvests.
In fact, most so-called mummy wheat was modern varieties or varieties that did not exist in Ancient Egypt; or a completely different crop. (The appearance of maize among the new crop must have been a dead giveaway, though these days it would still give comfort to those who fancy mystical ancient links between the Egyptians and the Mayans.)
Crafty local guides would have realised they were onto a good thing hiding ("planting") some sowable corn in their patches of pyramid just before the European visitors arrived. A more innocent explanation for some seeds that did exist in modern Egypt was the straw used for packing the shipments overseas. In one case, a gardener in England admitted that he had added good new grain to what his master had raised (brought back by an impeccably eminent Egyptologist), to avoid disappointing him.
Recent experiments show that seeds can survive for a while; over a century, anyway, and in cool, dry conditions with little fluctuation of temperature. Experiments at Kew Gardens showed that a constant 16°C could preserve one in a thousand seeds for more than 200 years. But even deep inside the stillness of the Pyramids, temperatures went much higher than that, and grain would be destroyed internally in a much shorter time.