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r fruit and vegetables, and effects, too may possess special diagnostic values, showing the need of trees, and therefore also the need of soils on which they are grown. Investigators are constantly confronted with determining whether foliage shows symptoms of disease or starvation, and whether this is due to a deficiency or an excess of any particular nutrient; whether fungicides inhibit the generation of fungi from the spore state, or whether the plant is fortified from sprays or dusts to become disease resistant, or repellent. Fungicides are valueless where plant disease is caused by bacteriae which invade the water conducting tubes, (roughly corresponding to the blood vessels of mammals), of plants, tree trunks, etc. and prevent the flow of water and nutrient solutions from roots to leaves. Deprived of water and nourishment, the plants or trees will wilt and die. Where, however, soils furnish these plants with protective inorganic nutrients, such as manganese, copper, iron, zinc, borax, etc. these bacterial diseases are prevented. Similar actions may take place in leaves. Deficiency Symptoms. Kodachrome Slides. Many acute deficiency symptoms have been identified by authorities and photographed, and I am able to show Kodachrome slides of the following: Manganese starvation on Swiss chard, spinach (five illustrations), courtesy of Dr. Robert E. Young, Waltham, Massachusetts. Apricot, sweet cherry, lemon, onions, peanut, soybean (two illustrations), tobacco (4 illustrations), sugarbeets, walnuts, wheat, all by different authors. Manganese deficiencies in Indiana on soyabeans, hemp, corn, by courtesy of George H. Enfield, Purdue University. Manganese on beets (mangels), (4 illustrations), and Romaine lettuce, Nassau County, Long Island. Courtesy of Dr. H. C. Thompson, Cornell University. Many more are published in "Hunger Signs of Crops," an illustrated reference book popular with scientific farmers and growers[13]. Other deficiencies that have been observed on nut trees are the so-called "little leaf" or "rosette" of pecans and black walnuts[14], which is due to a lack of zinc. Strangely enough, healthy orchards in this case contained a preponderance of fungi, whereas in affected orchards the soil microflora was predominantly bacterial[15]. We now have definite experimental evidence that lime, manganese and zinc are required in appreciable quan
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