Hi plantas(!),
Are you referring to the very first leaves to open from a seeds,known as the embryonic leaves(cotyledons) or the first true leaves to open above the embryonic leaves(?)...
Does the 'black' that you see look like healthy tissue or dried out and not healthy...
If you are able to post a photo,that would be helpful...
TTY,...

They seem to be Cotyledons', looks like healthy tissue, newly born, I checked them today and noticed some of the black tips are falling off and they are looking more like normal leaves. This is a white morning glory.I been reading up on this, and learning that, some plants can be weird, if we don`t know what we`re growing.
Thank you for responding to my question.