I think that the plant you are looking for is "Lucky plant" aka "Lucky Bamboo".The botanical name is Dracaena sanderiana and in a few days time, this plant will be seen everywhere here...
Rose-Marie

Here is a link that might be useful: lucky plant

I think you are talking about a rare vegetable even in China. It looks just like black air, hence the name Fah Cai, which means hair vegetable. In Chinese Fah Cai could also mean making a lot of money, so that is where the name prosperity plant comes from. I have had it once. Heard that it grows wild in the western part of China. Since people harvest it for money from the wild, they have done a lot of damage to the local flora.

Notocaceae
Nostoc commune var. flagelliforme Born.et Flah.

The second half of this page talks about Nostoc flagelliforme.