Seedless watermelon is not completely without seed coat. You look closely at the flesh of the seedless watermelon, you will find that in the ordinary watermelon long seed parts have traces of seeds, and even some chaff, these chaff is because the parent chromosomal incongruity did not normal fertilization formation, although there is no seed kernel inside, but there is still a seed coat. Measuring whether it is a good seedless watermelon parent one of the important indicators is the formation of chaff to be less, and chaffed seed coat can not be hard

You do the question on the right, there is seed coat. It's just that the seed coat is poorly developed and very thin and soft