Stomatal Patterns of Dicotyledons and Monocotyledons

After studying 443 species (226 dicots and 217 mono- cots) of 152 genera in 96 families, we have attempted to analyze the cuticular imprint differences between the two major groups of phanero- gams. Ten species were used in a statistical analysis of the variation of stomatal size and frequency. Eleven species are illustrated by photo- graphs of the plastic imprints of the cuticular characters. These were selected to represent trees, woody vines, suffrutescent, herbaceous and aquatic dicotyledons. The only monocotyledons illustrated are those with net venation. A brief key is presented to emphasize the differences as well as the exceptions. The authors conclude that in dicotyledons the stomata are usually of four or more ages and sizes, and that size is an unreliable taxonomic character. In contrast, stomatal size in monocoty- ledons is relatively reliable, there being a single size class for each species. No two genera of the 152 studied were alike in their cuticular char- acteristics.