Morphology Diagnostic features
C. serrulata has, like C. rotundata a smooth, herbaceous (if a little more robust) rhizome system, which produces short, erect shoots often with fibrous rootlets at each node, each shoot bearing 2-5 leaves. Unlike C. rotundata the leaf sheath of C. serrulata is broadly triangular and narrowed at the base. It is often a purple colour in the living plant. When shed, the sheaths leave open circular scars on the shoot. A ligule is present. The leaf blade is linear to somewhat curved, 6-15 cm long and 4-9 mm wide, with 13-17 longitudal veins. The leaf is narrowed at the base and the leaf tip is bluntly rounded and distinctly serrated. Tannin cells are present in circular-shaped groups. Phenotypic variation is generally minimal.
Shoot with distinctive open leaf scars, i.e., scars are not continuous around the shoot. Triangular, flat leaf sheath. Fibrous roots on shoot. Serrated leaf tip.13-17 longitudal leaf veins.
Thalassia hemprichii
C.serrulata is commonly confused with this species, however it may be distinguished by differences in the shape of the tannin cell aggregations - round in C.serrulata, rod-shaped in T.hemprichii. More conspicuous are the rhizome differences. T.hemprichii has a rhizome with scars between successive erect shoots while the rhizome of C.serrulata is smooth between shoots.
