Whether or not the story is true, the symbolism of the thistle (ahem, sorry for the pun) took root and is honored to this day. Other facts about the thistle include that it is a biennial plant, meaning it takes two years to complete its life cycle. It reseeds easily. It's a combination of beauty and ruggedness. It has a spreading, invasive root system, hence its classification as weed.
imprinted gene, a gene whose expression has been affected by genomic imprinting so that only a single allele functions, the other being turned off by epigenetic mechanisms during embryonic development.
The best known form of imprinting is filial imprinting, in which a young animal learns the characteristics of its parent. It is most obvious in nidifugous birds, who imprint on their parents and then follow them around. It was first reported in domestic chickens, by the 19th century amateur biologist Douglas Spalding.