Pollen grains of almost 1000 species were examined and measured to test four predictions: (1) “Primitive” angiosperms will have pollen that is starch-containing at the time of anther-dehiscence; more advanced families will have starchless pollen. (2) Where Hymenoptera and Diptera use pollen nutritionally, there will be selection of starchless (oil-rich) pollen, particularly where pollen is the only reward for visitors. (3) Conversely, in autogamous species, anemophilous species, and those pollinated by Lepidoptera or birds who make no nutritional use of pollen, the energetically more economical accumulation of starch will be seen. (4) Small pollen grains will be more likely to be starchless (oil-rich); starch-containing grains will tend to be larger.© 1979 Taylor & Francis Group, LLC.