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