Observations on developmental and structural aspects of stomata in six succulent species ofSenecio (Compositae)

The development and structure of stomata on the succulent leaves of six species ofSenecio are reported. It was found that in all the species investigated the development of stomata was of the mesogenous type and the structure of the stomata was anisocytic. The constancy in the development and structure of stomata in all the species of the genus investigated agrees with the view that a stomatal type and its developmental modes are constant at the genus level. Abnormalities such as contiguous stomata, degenerated guard cells, abortive and single guard cells are also recorded as natural phenomena.