Alimentary canal rarely coiled, occasionally with glands which are simple caeca and sometimes serve as air reservoirs; jaws often present and an eversible pharynx.
In such cases the vascular system is said to be polycyclic in contrast with the ordinary monocyclic condition, These internal strands or cylinders are to be regarded as peculiar types of elaboration of the stele, and probably act as reservoirs for water-storage which can be drawn upon when the water supply from the root is deficient.
Several remains of reservoirs exist; one very large one is now called Piscina di Cardito.
In Arizona, Mexico and Peru, reservoirs and aqueducts prove that hydrotechny was understood.
The cenotes or underground reservoirs were the important factors in locating the ruins of northern Yucatan.