A STUDY OF THE EFFECT OF H-ION CONCENTRATION ON THE GROWTH OF AGARICUS CAMPESTRIS

It has long been known that Agaricus campestris, the common mushroom, grows well on horse manure which has been partially decomposed. In order for fruition to occur, however, the manure must be covered with a thin layer of soil shortly after a good mycelial development has been obtained in the manure. Under these conditions mushrooms develop and mature over a period of several months. At the end of that time, however, the production ceases and before the medium has been depleted of nutrients. The cause of this may be the exhaustion of some food or food material, a change in the physical substratum, the formation of a toxin, or a change in the reaction of the medium. Then again it may be due to a combination of these and possibly other factors. In order to make a study of any single factor affecting the growth of mushrooms, it is highly desirable, if not imperative, to grow mushrooms in pure cultures. Very little investigational work has been done on the growing of mushrooms in artificial media. Several French investigators, notably Boyer ( 1 ) , have grown the mycelium on agar containing plant decoctions, Boyer found that the best growth was obtained where carrots, finely ground, were used as the basis of the culture. Duggar (2), and Ferguson (3) also successfully grew mushrooms on synthetic cultures of known composition, although they did not attempt to carry their experiments any farther. The object of this experiment was to determine, if possible, the optimum H-ion concentration for the growth of the mycelium of Agaricus campestris and to determine the effect of the organism upon the reaction of the nutrient medium.