I've been eating lychee fruits recently and noticed that every once in a while (in about 1 of 10 fruits or so) the seed in the fruit is shriveled, while in other fruits from the same batch the seeds have regular ellipsoid shape:
Top: regular seed, bottom: shriveled seed
The fruits with the shriveled seeds don't look or feel or taste any different from those with the regular seeds.
It seems like a binary trait, i.e. seeds are not more or less shriveled, they are either shriveled or not.
Why are the seeds so different? Do they come from different cultivars, or it's some kind of Mendelian development, or maybe some kind of a plant disease?