Comments on the Morphological Characters

7. Leaf whorls ("Axillary dwarf shoots").- All but the first of the members of each leaf whorl in H. gardneri may arise from one or more short shoots with annular insertion on the long shoot (Goebel, 1913; Rutishauser, 1983) or alternatively, they may be intercalary leaves produced from a meristematic ring below the shoot apex (Rutishauser, 1983). By either interpretation, the leaf whorls of this species are a unique feature of this taxon and the coding employed in Eckenwalder and Barrett (1986) is retained.

8. Stipules.- In Pontederiaceae, the structures variously described as stipules or ligules are outgrowths of the lower leaf zone above the insertion of the upper leaf zone (Richards, 1980). Confusion over whether to call these structures stipules or ligules appears to have arisen from an historical precedent set by de Candolle that monocotyledons do not have stipules (Richards, 1980). As defined by Richards, "stipule" includes the "ligule" of grasses, the tonguelike outgrowths between sheath and blade. Although less elaborate, such ligules are developmentally homologous with the stipule in Pontederiaceae, and are therefore coded identically (state 0). Heteranthera dubia and H. seubertiana possess ligulelike structures, and the leaf whorl members of Hydrothrix gardneri have stipules (Rutishauser, 1983).

9. Petiole.- Character state 2 is a new state that indicates petiole absence.

11-15. Leaf blade characters.- These refer to the blades of adult, petiolate leaves where these are produced, or to the blades of adult, sessile leaves where not. The boundary between petiole and lamina is not sharp in Eichhornia sp., but this did not unduly interfere with assignment of leaf-blade character states in this species. The filiform leaf of Hydrothrix gardneri has no structures that are obviously homologous to a petiole or leaf-blade, and so characters 9 and 11-15 are treated as missing data (?) for this taxon.

12. Maximum length of lamina ("Maximum leaf size").- Character states: 0 = 5-10 cm; 1 = >10 cm; 4 = <5 cm. These are modifications of the ranges given in Eckenwalder and Barrett (1986).

16. Inflorescence type.- Character state 2 refers here to a spike or raceme, 3 to a subumbel or umbel, and 4 to a two-flowered pseudanthium.

20. Peduncle pubescence.- Taxa are coded as hairy (state 1) if any part of the inflorescence axis is pubescent.

21. Flower attachment.- The pedicellate coding (state 0) is employed here if at least some of the flowers in the inflorescence have pedicels.

22. Flower number.- The flower count for Philydrum lanuginosum refers to the entire panicle, not each spike.

33. Stamen diversity.- Hydrothrix gardneri has a single fertile stamen and two staminodes and Philydrum lanuginosum has only a single stamen. This character is coded as missing (?) for these taxa.

43. Anther dehiscence.- An additional character. State: 0 = regular; 1 = poricidal.