We are all familiar with the mushrooms which you can buy from the local supermarket. These may be restricted to the common button mushroom and the better flavoured Swiss brown and Portobello mushroom although in Asian supermarkets there might be a dozen or more species on display: shiitake, dong gu, enoki, oyster, straw, etc. Unless you happen to do your shopping in Harrod’s or a European open air or covered market, the mushrooms on display will not have been been picked from the wild but produced in possibly huge factories that turn sawdust, straw, chicken or horse manure and other ingredients into fungus. These are the saprobic mushrooms which get their nutrients from dead plant material. So the closest the “forest mushrooms” you had on your plate at the restaurant the other night got to a forest was the sawdust they were grown on. This is a huge industry worth ten of billions of Euros annually. China alone produced about 14 million tonnes of saprobic mushrooms in 2006. But there are two other types of mushrooms as well - the parasitic mushrooms and the mycorrhizal mushrooms. The first of these draw their nutrients from living plants or animals. The vegetable caterpillar is one of these known in China as dong chong xia cao (winter worm, summer grass or Ophiocordyceps sinensis). This is one the most sought after Chinese herbal medicines and huge prices are paid for it. The third group of mushroom are produced the mycorrhizal fungi. There are estimated to be about 20,000 species of these fungi which grow in an intimate association with the roots of certain trees and about a quarter of these produce various kinds of mushrooms. Most of these are inedible while a few are deadly poisonous. However, about 1000 species produce edible mushrooms some of which are the most expensive foods the world has to offer. The relationship between the fungus and its host plant is so close that only one species has been produced away from its host tree and only a dozen other species have been cultivated in specialised plantations. As a consequence supplies of the vast majority of mycorrhizal mushrooms are only available by collecting them from the wild.