Mushroom spawn is any material that has been inoculated with mycelium and used as a carrier to transfer the mycelium to a growing substrate. Originally, mycelium was transferred by taking a growing substrate such as straw based compost or wood chips from one crop and used to initiate the next crop, however this proved to be a rather inefficient method and carried with it both pests and diseases. With the development of grain spawn by Dr. James Sinden in the 1930s growers were assured of a pure, disease free culture that could be easily distributed throughout the growing substrate. This delivery method is still in use today, but has developed into a sophisticated system where the grain used may vary from rye to millet to milo, depending on the needs of the grower. More recently, non-grain based delivery systems have been developed to reduce the likelihood of infections, speed up the growing process and add nutritional benefits to the growing medium.