An artificially produced plant species, Ehrharta erecta, is established in a natural environment.

Biologists Colin MacCleod, Oswald Avery, and Maclyn McCarty provide evidence that DNA and not protein in chromosomes is responsible for heredity.

The U.S. military uses the insecticide DDT to eradicate body lice among troops and civilians.

Ralph Wyckoff and Robley Williams develop the metal-shadowing technique, permitting three-dimensional photographs with the electron microscope.

1 Mar.

The Manhattan Project laboratory at Oak Ridge, Tennessee, produces the first milligrams of plutonium.

Nov.

Grote Reber publishes the first radio-contour maps of the universe.