Double Coconut (#173)
If I here double coconut, my association is usually dessert. But the double coconut is actually a seed. In fact, it's the largest seed in the world and can weigh up to 25kg. The double coconut tree only grows on two small islands of the Seychelles and is nowhere else found in the world. Unfortunately, it's considered an endangered animal species.
Also, it looks like a butt.
Let's dive into some evolutionary hypotheses, how such a huge seed evolves. First, the jungle there is quite dense and a tree needs to get big to finally get it's share of sunlight. That means, the tree needs enough nutrients to be able to grow for a long time, and a big seed can provide it. Secondly, if there aren't animals to eat and distribute the seeds, the seeds will just fall down more or less at the same place, close to the "mothertree". In order to avoid too much competition, it's beneficial if there are only a few seeds. And the fewer the seeds, the bigger they could get.
Probably, the ancestor tree had already quite large seeds, which happened to land on the Seychelles. Because of the lack of dispersing animals there, the seeds could grow ridiculously large.
So much for the size. I haven't found any scientific explanation for why they look like a butt though, sorry.
https://www.kew.org/read-and-watch/double-coconut-largest-seed-in-the-world