Aeschynanthus acuminatus（芒毛苣苔 ● Acuminate basket vine）

Aeschynanthus acuminatus is a climber found on rocks besides steams. The species is quite common in dense and mature forests all over Hong Kong. The plant is characterized by its thick and opposite leaves and its somewhat white branches.

A. acuminatus flowers in winter or early spring. In this February, I took a hike in the Tai Mo Shan area and met a colony of the plant. Unfortunately, the flowers are half-withered but I still managed to take a few pictures of them. After some comparison with the photos on the internet, I made some interesting observations and hypotheses.

Observations:

1. The flowers have a quite peculiar shape with didynamous stamens extending way out of the corolla tube.
2. The female reproductive structures mature after the stamens wither.
3. The drawing and description in Flora of Hong Kong suggests that the stamens are longer than the pistil. In reality, the pistil will elongate after the stamens wither to the original position of the anthers.
4. The withered stamens seem to contain some kind of viscous liquid after it withers; I suspect that the liquid is some kind of nectar, but I'm not sure whether it is secreted by the stamens or did it simply flow out from the flower.

Hypotheses:

1. The flowers should be insect pollinated 
2. The anthers stick the pollen on the abdomen of the pollinator. After the stamens wither, the stigma elongates to collect the pollen from the same position of the pollinator.
3. Guaranteed cross pollination by different maturation periods of male and female reproductive structures
4. Judging by the position of the stamens and the elongated pistil, the pollinator should have a fairly large body size. The winter flowering time and its mature forest habitat limits the choice, probably bees in the genus Bombus?

*Update: after further discussion is hkwildlife,net, it was suggested that the elongated pistils have already been fertilized. The possibility of pollination by birds can also be explored in the future. 

Here are some photos showing the withering flowers. Hope I'll meet fresher flowers and the plant's pollinator next time.

Pistil elongated flower

Cropped image showing possible nectar secretion

Front view of flower

leaves

Sophora tomentosa（絨毛槐 ● hairy sophora）

Sophora tomentosa is a tall shrub species that can be found on beaches and places near the coast. The speices is rare in Hong Kong and can only be found in several outlying islands or beaches in the Sai Kung district. Although rare locally, S. tomentosa is distributed worldwide. The shrub is characterized by its dark green compound leaves with recurved leaf margins. The leaf shape and the hairs on the leaf may be used by the plant to tolerate the rather harsh conditions near the seashore. The plant produces yellowish green pods in winter, the shape of the pods gives the species and its varieties another name -- the necklace pod. I am quite curious about how the pods disperse. They seem too large for a bird to consume, maybe the pods could float on the sea across outlying islands? I will try to examine the pods next time I see them.

Flora of Hong Kong states the flowering period as mid-summer and the fruiting season as winter, but flowers and fruits are both observed during my visit to the plant in mid-December. Here are some photos taken from a beach in Sai Kung.

Plant on sandy beach

Dark green leaves

Hairy abaxial leaf surface

Yellowish flowers 

Yellowish flowers

Necklace-like pods

Necklace-like pods

Portulaca pilosa（毛馬齒莧 ● Shaggy Purslane）

Portulaca pilosa is a herbaceous plant occasionally found near seashores in Hong Kong. According to Flora of Hong Kong, the species are found in sandy places near by the sea. P. pilosa is featured by its terete leaves and clusters of long hairs in axils of leaves. These characteristics are very likely adaptations to survive in a dry environment. The clusters of long hairs may reduce the transpiration of young leaves emerging from a shoot. The terete leaves, which are commonly found in xerophytes in deserts, can reduce the surface area to volume ratio. The plant also has a visible, beautiful network of veins in the thick leaves supporting the survival of the cells.

P. pilosa, among with species such as Sesuvium portulacastrum, Scaevola hainanensis, Tetragonia tetragonioides,  Suaeda australis, and other plants living in the seashore all have thick leaves, waxy cuticle, and relatively small flowers. As the discussion in (HKWildlife.net) suggests, this may be an example of convergent evolution in which various species adopt similar physiological features under similar survival pressures.

The photos below are taken on a hill in the New Territories. Interestingly, the population lives far from the seashore and besides a cement road. Given there are man made objects and construction going on near the site, my hypothesis is that the seeds of plant may be brought up in the delivery of construction materials.

Whole plant

Shoot, showing leave veins and white hairs

Pinkish flower, an ant seems to help pollinating it

Another flower
The structure at the right of the flower is a fruit with seeds gone

Geissapis cristata（睫苞豆 ● Geissapis）

  Geissapis cristata is an annual herb that grows in certain wetlands in Hong Kong. It seems quite uncommon locally with restricted distribution. The species is characterized by its large bracts with cilia. The bracts probably brought the plant its Chinese name, which means bracts with eyelashes. Personally, I think the bracts are used by the plant to protect the flower buds and other fragile structures from insects and other pests, but I wonder whether the structure would hinder seed dispersal too since the bracts also seems to be covering up the pods. According to Flora of Hong Kong, the pods have 1-2 segments with each segment 4mm in length. With pods this size, it is possible that the plant depends on anemochory (wind dispersal). Maybe the bracts could prevent the seeds from being blown away when the wind is not strong enough to bring the seeds to a place far away, but further studies are needed to test this hypothesis.

  I found a population of G. cristata in a piece of wetland near the seashore in Sai Kung. The location is under heavy pressure  for development and this population may very likely be completely wiped out if the development plan is implemented. It occurs to me that wetlands, with its flat nature, is extremely vulnerable to development, and sadly the government hasn't done much to protect them. It is really a pity to see that more and more wetlands with high ecological value are replaced by residential flats and houses. I really hope to see more laws and regulations targeting the protection of wetlands such as this one in the future, or else, rare wetland species such as G. cristata will very likely become locally extinct in coming years. Here are some photos of G. cristata taken in November.

Population

Leaves

Yellowish flowers

Bracts

Salomonia cantoniensis（齒果草 ● Salomonia）

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.

Population with white flowers

White flowers with no purple pigment

Leaves and stem of the white-flowering population. Stems are winged

A normal spike with purplish flowers

Purple flowers, the structure below are the capsules 

Winged stem of the purple-flowering population

Rhododendron championiae（毛葉杜鵑 ● Champion's rhododendron）

Rhododendron championiae is a shrub or small tree that has restricted distribution in Hong Kong. According to Flora of Hong Kong, the species can only be found in limited localities including Tai O, Ma On Shan, and Victoria Peak. Personally, I've seen the population growing in Tai O and the one on Ma On Shan. The species seems to be growing in shrublands on steep slopes. The species is characterized by its glandular hairs growing on leaves and buds, an adaptation probably used to save water and prevent insects from eating the tissues of the plant. In spring, white flowers with yellowish dots and occasionally having a touch of pink color emerge. The fruit of the plant is a capsule that holds the seeds before they are distributed by anemochory like other Rhododendron spp.. The photos below show withering flowers of R. championiae in Tai O (I was a little too late).

Flowers

New leaves

Old leaves (crowed towards the apex, in a whole like arrangement)

Flowers

Flowers

Flowers

The whole population on the slope

Utricularia caerulea （短梗挖耳草 ● Blue bladderwort）

Utricularia caerulea is a small carnivorous plant that grows in wet environments. The species is particularly common on wet rocks near streams, commonly found with other Utricularia spp.. The ecological niche of the species is somewhat similar to that of U. bifida. Both plants are usually not submerged and growing in relatively drier habitats near streams. U. caerulea bears flowers in late summer, autumn, and winter. The species has two different flower colours, white and purple. Both variations are quite common in Hong Kong. I found populations of white flowers in a few sites in Sai Kung and on Lamma Island. While I observed populations with purple flowers in Tai Lam, Hong Kong Island and in another site on Lamma Island. Surprisingly, the two varieties doesn't mix together. The two sites on Lamma Island are only a few kilometers apart but plants in a site is either purple or white, not both. It may suggest that different populations rarely cross pollinate, and the seeds do not travel far enough to another stream. Below are some photos I took in various sites.

Purple flowers

Fruits

Purple flowers

Purple flowers

Population with purple flowers only

White flower

Population with only white flowers

The damp soil in its habitat