National Geographic : 1950 Apr
© National Geographic Society 4' A Kew Museum's Gums and Resins Resemble Candies in a Store Window Forty centuries ago gum arabic collected from sick acacia trees went into Egyptian paints and cosmetics. Today vegetable gums go into paints, inks, pharmaceu ticals, "frostproof" concrete, and other products. Shel lac, an insect excretion, is used in plastics and varnishes. iodtachromes by B. Anthony Stewart " Iris Petals Turn to Gold, Blue, Red, and Green in the Chemist's Beaker A simple test to determine chemical pigments is made in Kew's Jodrell Laboratory by Dr. C. R . Metcalfe (left) for the sake of the camera. The laboratory's research into the anatomy of plants has thrown new light on their scientific classification.