Romulea rollii

Morphological description

Romulea rollii is a small perennial herbaceous plant belonging to the family Iridaceae, recognizable by its biological form as a bulbous geophyte. The height ranges between 10 and 25 cm. The underground system consists of an asymmetrical ellipsoid corm about 10-15 mm long, with brown tunics that tend to peel off at the apex.

The flowering stem is relatively short, generally shorter than the leaves, and in the upper part is epigeal, while the base is hypogeal (underground). The leaves are two, basal, short and sheathing, while the cauline ones are longer, with a length ranging from 15 up to 35-40 cm, thin and subcylindrical, about 0.7 mm in diameter. They are arranged prostrate on the ground and present a characteristic quadruple groove, typical of the genus Romulea.

The flowers are solitary, protected by a subacute bract with a hyaline margin and a membranous bracteole with an herbaceous median nerve. The perigonium, measuring from 15 to 22 mm, is composed of six elongated-lanceolate lobes of white color, sometimes with lilac shades, with darker streaks. The throat of the perigonium is yellowish and slightly hairy, a distinctive characteristic of the species. The stamens are about half the length of the perigonium, with hairy filaments and yellow anthers; the style is generally shorter than the apex of the anthers, a trait that distinguishes Romulea rollii from some related species.

The fruit is an ellipsoid capsule approximately 5 × 7 mm in size, containing spherical brown seeds.

Habitat and distribution

Romulea rollii is a typical species of the Italian Tyrrhenian coasts, with reports mainly in the provinces of Pisa and between Argentario and Maremma, in Tuscany. The species prefers sandy habitats, particularly dune fields and predominantly coastal moist sands, but can occasionally be found also on river sands. It grows at low altitudes, in environments characterized by loose and well-drained soils, generally exposed to full sun or slight shade conditions.

In the Mediterranean context, the genus Romulea counts about 90 species with disjunct distribution, with a main center of diversity in the Cape region and a second in the Mediterranean-Atlantic basin, to which Romulea rollii belongs. The central geographical position in the western Mediterranean favors genetic exchanges between different populations, facilitating processes of hybridization and speciation.

Flowering period

The flowering of Romulea rollii occurs mainly between February and March, a period that coincides with that of many other species of the genus. This temporal synchrony of flowering favors the possibility of natural hybridization among related species coexisting in the same habitats.

Ecology and pollination

Like many species of the genus Romulea, R. rollii also presents marked phenotypic and genotypic variability that can be linked to adaptive reproductive strategies. The flowers, with their distinctive structure and color, are probably pollinated by pollinating insects attracted by the combination of white with yellowish details in the throat of the perigonium. The hairiness present on the staminal filaments may facilitate pollen transport.

Pollination is presumably entomogamous, with insects moving among species flowering simultaneously, also favoring natural hybridization processes. Seed dispersal occurs through the capsule which opens at maturity, releasing spherical and brownish seeds, probably destined to remain near the mother plant, adapting to colonize the sandy soils of the coasts.

Curiosities and traditional uses

No ethnobotanical, medicinal applications or specific food uses are known for Romulea rollii. However, the genus Romulea in general is little studied from this perspective, and Mediterranean species are often appreciated for their ornamental value, especially for the delicate flowers that resemble those of saffron, from which the common name "little saffron" derives.

Etymology

The generic name Romulea probably derives from Romulus, the legendary founder of Rome, perhaps due to the abundance of some species in Italy or for a classical suggestion linked to Mediterranean flora. The specific name rollii is a tribute to the Italian botanist Giuseppe Rolli, to whom the species is dedicated.

The Italian common name "zafferanetto di Rolli" recalls the resemblance of the flowers to those of saffron (Crocus sativus), although it is a different species, and acknowledges the dedication to Rolli.