The branchlet of Casuarina has a glabrous (Division Gymnostomae) to pubescent (Division Cryptostomae) epidermis. A sclerenchymatoul hypodermis is present which, in several species, is continued into the inner layers of the internodal ridges as T-beam-shaped masses. Photosynthesis is mainly carried out by the mesophyll in the internodal ridges.

The evaluation of characteristics of the vegetative structures supports the accuracy of Poisson's observations. Two main subdivisions, which correspond to Poisson's Cylindricae seu Cryptostomae and Tetragonae seu Gymnostomae, need to be set apart. The two taxa certainly could be represented by separate genera and the term "division", applied by Poisson, is inappropriate and should be dropped.