Cur open a ripe avocado the other day and it had black fibrous tube-like strands running through it. They looked like the black of a bruised banana but when poked they were quite firm and when pulled would pull out like the hairs of a coconut. I had a bite and the thing tasted okay but I was put off by the fibres.
What were they?
Were they running all through the pulp, or just through a part? Were they coming out of the seed?
Black stripes are normal when some varieties of Avocado get overripe. The smooth skinned Florida variety is more prone to this than the pebbly skinned Haas avocado.
I have noticed these black threads often as well. It seems indeed a sign of being overripe.
I usually throw these avocado’s away, not because of the threads themselves but because they are an indication the green flesh will have become too soft for my liking.
Does that mean that it’s started growing?
PS: pravnik Are you a lawyer or did you mean travnik ?
Ano, flapcatse, ja jsem americky pravnik!
(translation for mods: Yes, flapcats, I’m an American lawyer!) 
Re: “travnik”…heh heh! I’ll change it to that if I ever get disbarred. 