THE PLANT WORLD 269 



diseases. A complete series of the various stages of growth of the 

 bitter-rot fungus is shown ; also various forms of the smut diseases of 

 grasses, the leaf-spot on the sugar beet, and the black-knot of plum. 



On a separate rack next to this case are about forty different forms of 

 leaf diseases of agricultural crops. In each instance a brief description 

 of the particular disease accompanies the specimen, and recommendations 

 as to how such disease may best be combated are given in most instances. 

 Growing cultures of various fungi are shown. 



Timber diseases. — The case devoted to timber diseases contains a 

 varied collection of diseased woods, showing the manner in which various 

 timber-destroying fungi bring about the decay of living trees. Several 

 large punks or fruiting organs of these fungi are shown growing on living 

 trunks. 



Sugar beets. — A third case is devoted to an exhibit of sugar beets 

 prepared by Dr. C. O. Townsend. The various stages in the develop- 

 ment of the sugat beet, from the seed to the mature beet, are shown ; 

 also the various steps in the preparation of the products and by-products 

 of the sugar beet. 



Nitrogen-fixing bacteria. — A fourth case, prepared by Dr. George T. 

 Moore, illustrates the relation of bacteria to the fixation of atmospheric 

 nitrogen. In the lower part of the case, on one side, is shown the 

 method of isolating the bacteria from nodules on leguminous plants and 

 making poured plates ; transferring the organisms to nitrogen-free silica 

 jelly and to nitrogen-free liquid media ; saturating sterilized cotton with 

 this culture ; drying and packing the cotton ; together with packages of 

 nutrient salts for making up the fresh culture liquid, and wrapped pack- 

 ages ready to mail to applicants, thus illustrating the preparation and 

 distribution of these organisms in general farming by the Department of 

 Agriculture. 



On the opposite side of the case are illustrated the process of prepar- 

 ing the culture, the inoculation and drying of the seed, and all steps 

 necessary previous to sowing or storing the seed. Herbarium specimens 

 of some of the various leguminous crops are exhibited, with special com- 

 parison of inoculated and uninoculated plants, to demonstrate the benefit of 

 nodule-forming bacteria. Some photographs are also included in this 

 exhibit. 



Mushrooms. — The mushroom case, prepared by Dr. B. M. Duggar, is 

 illustrative of the work in mushroom growing, and has been designed 

 with the view of giving a general exposition of the mushroom industry 

 and of the scientific work which is being done rationally to stimulate this 

 industry. 



On the lowest shelf are shown the two types of mushroom beds (the 

 flat bed and the ridge bed) in common use for the cultivation of Agaricus 

 campestris. The habit of the mushroom is shown by means of plaster 

 casts, each of these being a reproduction of a mushroom or a cluster of 

 mushrooms grown in the experimental beds at Columbia, Mo. 



Three shelves are devoted to commercial spawns, edible commercial 

 mushroom products — which, at present, are largely foreign — and views 

 of the mushroom industry in France and in America. Among the spawns 

 are to be found the English, the French, and the new American article. 



The products include nearly all species and grades of preserved mush- 



