These are quite exotic plants, which are easy to care for as long as they are not over watered. Also known as "Zanzibar Gem" they were not commonly available until recent years.
Zamioculcas zamiifolia, to give it it's full name, can tolerate most light conditions provided they are kept on the dry side. Exotic succulents with glossy green foliage.
This Zamioculcas is in an office on Grosvenor Gardens, in London SW1