Salomonia cantoniensis is a annual herb species that is widespread and common in Hong Kong. Populations of the plant usually occupy relatively dryer habitats in shrublands. The species is most common in sunny habitats. I have observed populations growing at roadsides and open habitats near country trails. This species is distinguished from the other similar species in the genus,
S. ciliata（橢圓葉齒果草）, by its winged stems.
S. cantoniensis bears purplish red flowers in the summer and capsules with a denticulate surface. The structure of the capsule makes me wonder what evolutionary advantage does a denticulate surface have. My guess is that although the plant may depend on wind or gravity to disperse its seeds, the denticulate surface can facilitate dispersion by animal fur or feathers so that the seeds can be transported to a further location once in a while.
Among a hike in NT east, I discovered a population which bears white flowers instead of the usual purplish red. This phenomenon is not described in
Flora of Hong Kong and some other sources. The unusual colour is probably due to genetic mutation or a recessive gene expression. The photos below are taken in NT east in summer.
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| Population with white flowers |
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| White flowers with no purple pigment |
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| Leaves and stem of the white-flowering population. Stems are winged |
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| A normal spike with purplish flowers |
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| Purple flowers, the structure below are the capsules |
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| Winged stem of the purple-flowering population |
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