What’s in the dish is called a “burl”. One of the keys to the survival of the redwood is its regenerative abilities, and one of these regenerative capabilities involves the growth of a burl. A burl is made up of dormant redwood stems, is covered in bark and grows when a redwood is cut, damaged, injured, or diseased. In addition, saplings may sprout from these burls and trees that grow from these samplings are genetically identical to the original tree.
The burl is kept in a wooden dish (or glass but I found wood to be much prettier) filled with 1/4-1/2″ of water. Only two weeks ago when I purchased it, the sprouts were barely a 1/4″. I suppose in the next year I’ll have to find a place outside or cut a hole in our ceiling. lol