Tuesday, 21 March 2017

Whatever you do, don't throw this Hoya into the briar patch

The way we remember Thomas Hoy, the 2nd Duke of Northumberland's gardener at Syon House, is through 300 species, and some varieties, of mostly waxy leaved creepers.

Hoyas were a novelty in London in the nineteenth century. They grow naturally across southern Asia into the Pacific Islands, with some extending into the Indian region. In Australia there are six native species, all but one extending into other neighbouring countries. 

In this blog in 2009, I was showing off the latest flowers on Wax Plant, Hoya australis. Growing below our decking in Sydney, this climbing vine enjoyed a nice humid and mostly shaded spot, with a little loving attention from time-to-time. The species is a popular plant in cultivation, and easy to grow, but it is just one subspecies of Hoya australis, called subspecies australis. It grows throughout the tropics of Australia and further afield, extending southward into north-eastern New South Wales.

There are four other subspecies: two (sanae, tenuipes) from Cape York Peninsula in Queensland and two from the Top End of Northern Territory, where I was visiting back in October 2016. One of the two Northern Territorian subspecies, oramicola, is found only in the Tiwi Islands, north of Darwin.

The other, rupicola (sometimes considered a separate species, Hoya rupicola) grows throughout monsoonal Northern Territory and in the nearby Kimberley region. I saw it at Litchfield National Park, near Tolmer Falls. 

Both Northern Territory subspecies lack things called colleters, a cluster of glands on the upper surface of the leave near to where the blade connects to its stalk. I gather you will find these in the more commonly cultivated subspecies australis, but I haven't been able to check yet. Thanks to Flickr image by Xylopia they look like this:

Hoya australis subspecies rupicola is a scrambler rather than a climber. In fact often it's little more than a couple of leaves among the rocks, looking as if they'd rather be somewhere else.  The highly succulent (chunky) leaves are good fit for this tough setting and you can see in this picture a stem heading out along the rocks to find another nook for its next cluster of leaves.

The name 'rupicola' means rock loving, or dwelling, and in the original description of this plant (as a species), botanist Ken Hill described rupicola as 'extremely succulent and drought resistant, growing in small humus accumulations usually on sandstone rocks, often in full sun'. Ken reminded us that this region (the monsoonal north of Australia) can have no rain for up to six months of the year.

But the plant is not foolish. In more sheltered places it can bulk up a bit, and one of the best places is scrambling under and around another species, as you can see here. .

*The title is an adaptation of the line used by Br'er Rabbit to escape being eaten by a fox. Brer and our hoya might imply they like the open ground but both thrive amid the undergrowth.

Tuesday, 14 March 2017

Maple Twist is no Monkey's Hand

Apart from the absence of red simian-like floral parts, Maple Twist makes me think of Monkey's Hand Tree. There's the big downy leaves (as above!), the chunky flowers with an ornate centrepiece and the soft fragility of the trunk and stems.

As it turns out, Pterospermum acerifolium is indeed closely related to Chiranthodendron pentadactylon (the scientific names being informative if a little cumbersome).  They both belong to what was once Sterculiaceae (think Brachychiton) and is now Malvaceae (think Hibiscus plus now Brachychiton). The flower turns out to be more different than I thought, but we'll get to that later, like I did when I discovered this plant in Melbourne Gardens.

Maple Twist is also called Dinner Plate Tree on account of the big leaves, which are in fact used to hold or to wrap less savoury things like tobacco. Where it grows naturally - India and southern China, southwards to the Malaysian Penninsular - it gets called Bayur Tree, Machukunda, Bayog, Kanakchampa and more.

Most parts of the plant, including the flowers, are used in India for traditional medicine, to treat ailments from cancer to small pox. In recent years there has been a steady stream of scientific papers (e.g.) demonstrating antibacterial, antioxidant and other medicinal activity in, particularly, leaves and bark. The flowers are mostly used in a tonic, for treatment of various internal and external wounds, while the downy hairs on the undersurface of the leaves are said to prevent bleeding (as well as provide a handy tinder for starting fires).

The leaves are, as the species name suggests, shaped like (large) maple leaves. In dryer climates the tree is deciduous for a short time. When I photographed our Melbourne Gardens specimen, growing among a fine collection of araucarias from New Caledonia, there were plenty of dry leaves on the ground below.

The white flowers, like the red flowers of the Monkey's Hand Tree, attract bats as pollinators. But close up, they are not remarkably similar (see my post from November 2013) . What I had thought - at a distance of a few metres (the flowers are high in the tree) - to be something like the monkey hand of Chiranthodendron turned out to be the main part of the flower, with petals. The sepals (the layer outside the petals) are pealed back in the mature plant, like a banana skin.

In Monkey's Hand Tree, the petals and sepals seem glued together (I called them, naively perhaps, simply 'sepals' in my 2013 post) around the centre-piece which often drops from the flower. In Maple Twist, the petals and inner parts are more likely to fall together to the ground. You can see some of the detail here, but remember I've had to photograph this from a distance. I'm assuming the inside bits of the flower somehow conjures up the 'twist' part of Maple Twist. Maybe.

What you can't see, or detect, is the flowers producing a soft perfume. Mostly at night as an extra attractant for those bats but it also appeals to humans - the spent flowers are used as a fragrance and deodoriser for stored clothes and linen.

The fruits are large and 'cucumber-shaped', but given they persist on the tree for up to a year and I could see none on ours, it seems our trees don't set seed. If they did, the seed would be winged, living up to the genus name which means exactly that (winged seed).

This is a tropical to subtropical tree, but from sometimes higher elevations where temperatures can be lower and rainfall higher. They tolerate a dry season of up to seven months so perhaps they'll survive conditions in Melbourne in 2090.

It's grown widely around the world but mostly in Asia and nearby, and seldom, I think, in Australia. At least in the south. Although they can grow in areas with low rainfall, they tend to do best near a water body of some kind. Our tree is next to the Nymphaea Lily Lake and its roots no doubt take advantage of that situation.

Note: I must thank Stuart Williams (@stuartwilliams_) for alerting me to this species. Stuart posted a picture of the flower on Twitter, 23 December 2016, later remarking that it was taken in Melbourne Gardens. Thanks to these tweets I tracked it down on our census, and to this specimen!

Tuesday, 7 March 2017

Californian fried eggs in need of ironing

Back in January, this poppy was a stand out in our California Garden, on the Anderson Street side of the Melbourne Gardens. Was it the yellow pom-pom of stamens in the middle of each flower, the soft, crinkled white petals floating in the wind, or the summery-grey leaves? Presumably the combination of all.

We have a couple of mature plants in the California Garden, and others in the rockery near the William Tell Shelter, and one in the Grey Garden near the Temple of the Winds. Tough locations with little extra water added.

Romneya coulteri is often called the the Californian Tree Poppy. It's a poppy (family Papaveraceae), from California (and Mexico) and compared to most other poppies it's tree-like (although lanky, it grows to over two metres high with a woody base).

The leaves are leathery and coloured waxy grey-green, as are many of the succulents sharing similar habitats in our botanic garden.

There are two species of Romneya, the other being just little smaller in flower and leaf size (both are considered naturalised in south-west Western Australia, with Romneya coulteri seemingly an escape from gardens in Perth).

With open flowers stretching to about 10 centimetres across, Romneya coulteri is the biggest flowered member of the poppy family and, along with Hibiscus lasiocarpos, the biggest flowered plant in California. So yes, the flowers are even bigger than those of the Himalayan Blue Poppy, Meconopsis betonicifolia, which they resemble apart from the petal colour.

The Californian Tree Poppy is also called the Matilija Poppy, after one of it's natural locations, a canyon 100 km or so north-east of Los Angeles, and Fried Egg Plant, after the resemblance of the flowers to a fried egg.

Poppies are well known from their crazy number of stamens (the pollen-bearing sticks surrounding the sticky female centre of the flower) and this species has 'very numerous'. I reckon there's about 300-400 stamens in each flower, almost as many as the wrinkles as I can see in its petals...

Tuesday, 28 February 2017

Yellow Gum and trousers hanging by a thread

A generally erect, straight trunked, stately tree, with mottled bark sometimes similar to that of River Red Gum, but more likely to have a cream/yellow tinge, and to grow a little uphill from wet areas.

That's how Bernard Slattery, Ernie Perkins and Bronwyn Silver describe the Yellow Gum, Eucalyptus leucoxylon, in their guide to the Eucalypts of the Mount Alexander Region. In case you are wondering, the Mount Alexander Region is Castlemaine and surrounding goldfield country, and that's where I met Ernie Perkins.

Ernie died last year and the little booklet is dedicated to him, 'teacher, botanist, field naturalist (1934-2016). Back in the day, Mr Perkins taught me chemistry at Castlemaine High School. He was also my tennis partner on weekends. More relevant to this booklet, however, I remember his A4 guides to the wattles, eucalypts and other bits and pieces of nature to be found around Castlemaine. They were always simple, succinct and accurate.

This book, published by the Friends of the Box-Ironbark Forests includes 12 common species and eight 'less common' species of Eucalyptus. In a section that Ernie must have written, is a guide to where you can find these species, and other eucalypts, in the streets of Castlemaine.

For example, my feature eucalypt, the Yellow Gum, can be found in McEwan St (outside numbers 4-6), Wheeler Street (outside number 7 - my grandparents used to live at 17), as an avenue planting in Elizabeth Street, in a copse in Yates Street, and in Kaweka Flora Reserve. 

The book reminds me of Leon Costerman's pocket guide to the trees of Victoria, first published when I was six (1966) and reprinted squillions of times since then (you can still buy it). In fact Leon very kindly provided his drawings to be included this Mount Alexander guide.

As to Yellow Gum, the variant found around Mount Alexander and generally more or less north of the Divide (even popping into NSW) is subspecies pruinosa. There are others in Victoria: subspecies connata, clustered around Port Philip Bay; subspecies bellarinensis, clustered, appropriately, around Geelong; subspecies leucoxylon in mostly western Victoria and across into South Australia, but reaching out a little into the north-east of our State; subspecies megalocarpa just popping into Victoria from South Australia, around Nelson, but widely planted for its big fruits and colourful red flowers; and, phew... subspecies stephanie in the deserts of western Victoria.

The differences are to do with a waxy bloom (or not) on the buds and fruits, plus the size of fruits, flower cluster stalks and leaves. Take a look at the key in VicFlora.

I can't confirm the nomenclature of the sprig featured in this post but I suspect it was modeled from a specimen of subspecies megalocarpa, or the difficult to classify cultivar 'Rosea'. It is made from thread, by embroidery wizard Lynne Stone. Lynne presented me with this artwork as a gift in thanks for opening 'A Secret Garden', the annual exhibition for the Embroiderers Guild Victoria back in October 2016.

I was able to spring a surprise on the group by revealing a set of Mueller's braces. Not quite holding up my trousers but, as the experts say, 'the braces are on fine canvas displaying floral motifs in cross stitch, in Berlin needlework style'. Sadly no Yellow gum in the motif, but at least I don't have try and identify the subspecies.

Tuesday, 21 February 2017

Cannon ball fruits in Mexico need horses, old or new

Shading the car park in George Brown Darwin Botanic Gardens is a tree with fruits that only a horse could break open. Or perhaps an animal now extinct in Mexico and Central America, the current homeland of the Mexican Calabash, Crescentia alata.

Yep, a trip to the tropics is fertile ground for a blogging botanist, although presumably the same applies to a tropical botanist slumming it in the temperate region for a few days. Anyway, I'm close to the end of my northern Australian obsession but I couldn't resist another exotic tropical species with a cute back story.

In a learned paper on 'the fruits the gomphotheres [now extinct elephant relatives] ate', Daniel Janzen and Paul Martin hypothesise that horses and cattle may now provide a decent substitute for extinct 'megafauna'. Not just these elephant relatives but perhaps extinct horse ancestors.

The Mexican Calabash, or Jicaro, is the only member of the plant family Bignoniaceae in Janzen and Martin's list of Costa Rican lowland plants with seeds 'probably dispersed by extinct megafauna'. There are quite a few members of the pea family, figs, palms and others.

Bignoniaceae includes well known temperate trees such as the Indian Bean (Catalpa) and Jacaranda, bearing flowers with the male bits (stamens) attached to the petals, and typically the whole flower looking a bit like a trumpet or vase.

The Calabash has a shy and crooked, bell-shaped flower, followed by a hard and heavy ('cannon-ball-like') fruit. Both arise directly from the trunk or stems, making this a cauliflorous plant.

Today introduced horses crack open the ripe fruit of the Calabash in their mouth, eating and then distributing the 200-800 seeds held within a slippery pulp inside. Tests showed that 97% of seeds extracted from the horse dung and washed would germinate.

In the absence of horses, the fruit rots on the ground during the wet season and the fermenting pulp kills the seeds. The fruit drops from the tree while still green then, over a month or so, browns and ripens, with the innards becoming black and slimy. Although the pulp is sweet, it was a 'fetid' odour.

It seems likely the tree is more common in Cost Rica today than it was historically, thanks to the free-ranging horses. One consequence of the plant going through a bit of a bottle-neck when the local horses died out might have been a reduction in some pollinating animals such as bats.

The flowers of the Calabash are visited by four different kinds of bat today, and their numbers and diversity may have suffered as the horses, and then the Calabash, declined. This in turn could have led to changes to other plants species that may have depended on these bats for pollination. Such a tangled web!

Tuesday, 14 February 2017

Showy Crepe Myrtle, pride of the tropics

Pride of India is a species of Lagerstroemia (Crepe Myrtle) from China, Cambodia, Myanmar, Thailand, Vietnam, Indonesia, Malaysia, and the Philippines. As you will have noticed, not from India, although there are numerous references (logically with a common name like this) to it growing in that country.

More reliably perhaps, a scientific paper on the reproduction of the species specifies its range in India as 'across the Northern Himalayas and Western Ghats'.

The increasingly commonly planted Crepe Myrtle in southern Australia is Lagerstroemia indica, definitely from India in this case - plus a few other nearby countries - although there are other native and exotic species available in horticulture. Most of them are bursting into flower across Melbourne as I write. All up there are about 55 species of Lagerstroemia, growing naturally in Australia, eastern Asia and through into Japan.

We don't grow Pride of India, Lagerstroemia speciosa, in the Melbourne Gardens but there is (or was) a specimen in Sydney's Royal Botanic Garden, and it is commonly grown in the tropics. You will see more often around Melbourne cultivars of Lagerstroemia x matthewsii, a cross between Lagerstroemia speciosa and Lagerstroemia indica, and various mixes and selections of this hybrid and the species. My pictures of the Pride of India are from outside a church in Darwin, Northern Territory.

The species name 'speciosa' means showy or spectacular. The leaves are big, for the genus, and the flowers certainly grab your attention. They are big and in a prominent flowering stem.

The petals are crumpled, as they are in most of the family Lythraceae - a family which also includes the Victorian (apparently) native, Purple Loosestrife (Lythrum salicaria), a vigorous plant of wet areas in both our Royal Botanic Gardens Victoria sites.

You might also notice this picture the many stamens - the male parts bearing yellow anthers full of pollen. Reputedly each flower has 130 to 200 stamens.

The fruit is a capsule, splitting to released winged seeds.

The wood of the species seems to be something of which we should be particularly proud. In India, where we'll say it's native, the wood is used for construction of furniture, buildings, boats and rail sleepers. The wood is tough, durable and water resistant.

Other parts of the plant have more transient uses such as the leaves being used to make a tea, leaf extracts being used as a insulin-like treatment for diabetes, and the fruits used - somehow - to cure mouth ulcers. Take care with this plant though - some parts are 'astringent', others are poisonous.

Tuesday, 7 February 2017

Cuddling up to the Brazilian Edelweiss

This is the kind of plant you want to cuddle up next to in bed. Although perhaps just its leaves rather than the large woody base.

It's called Sinningia leucotricha, or Brazilian Edelweiss due to its place of origin and its woolly leaves reminiscent of the mountain daisy of Europe.  Those woolly hairs are at their cuddliest when young. As the leaf expands the hairs become sparser because they remain the same in total number (per leaf). 

The flowers are softly hairy - downy - as well. They are clustered above a group of usually four leaves, and their pastel orange colour and long tubular shape have evolved to suit hummingbirds (or vise versa I guess).

At the bottom of the plant, but partly above ground, is a big woody tuber (the caudex). This is enough to get the plant grown by cacti and succulent enthusiasts. It grows naturally beside other succulents, in rock crevices or on steep hillsides.

Sinningia is a genus of about 60 species in the mostly tropical and subtropical family Gesneriaceae. The species of Sinningia are all found in Central and South America, with most (like Sinningia leucotricha) found in southern Brazil (in this case the State of ParanĂ¡).

The genus was named after a gardener at Bonn University, called William Sinning. Mr Sinning raised the first seed of what became Sinningia in Europe.

According to the Sinningia & Friends website there are a few cultivars of Sinningia leucotricha around, including some with two tiers of the four leaves, and some without the distinctive blotches you can see where the tube of the flower flares out with a few round lobes.

In nature the plant has become threatened with extinction due to uncontrolled collecting - due to the beauty of its leaves and flowers. To relieve this stress, attempts are being make it easier to propagate and get into cultivation. It seems that growing under full sunlight is not recommended and 60-70% shading will give you the best vegetative development.

We have just one plant in our nursery, and none out on public display. I must tell Chris Jenek, the hort technician looking after this plant, to move into the shad.

Tuesday, 31 January 2017

Such beautifully draped foliage but no leaves

Most wattles (Acacia) don't have leaves. Instead, the leaf stalk expands into a flat blade - which to all intents and purposes acts like a leaf - and any juvenile feather-like leaves at the end of the stalk are lost. We call this expanded stalk a phyllode.

Take a look at a local Blackwood, Golden Wattle or Coastal Wattle to see what a phyllode looks like. But not, for example, a Silver Wattle which has actual real feather-like leaves!

The species I've illustrated here (in the right of the picture above) has phyllodes that are particularly long, up to 20 cm long, but only a millimetre or two wide. It's as if the evolutionary instruction didn't quite get through. Instead of forming something like a standard leaf, it's become more like a conifer or she-oak.

There are advantages in having long, thin phyllodes, particularly where this plant grows, between Litchfield National Park and Darwin. When it's hot and dry it isn't always an advantage to expose lots of leaf(-like) surface. Far better to keep some of your foliage partly shaded, with less surface area exposed to the sun all day.

This may be a successful adaptation but as a species Acacia praelongata isn't doing that well. Its restricted a scattered localities in the top bit of the Northern Territory. So while up that way with my fellow heads of Australian Botanic Gardens in October last year we helped (I think) Ben Wirf collect some seed for the George Brown Darwin Botanic Gardens, part of the Australian Seed Bank Partnership.

There seem to be about 40 species of Acacia with leaves at least this long and sometimes this narrow, but the habit and habitat of Acacia praelongata are definitely unusual. A species called Acacia murrayana has similarly long phyllodes but grows in arid areas outside the tropics and those long phyllodes have a single nerve/vein, rather than three in our species (although I'm not sure what quite to count in this photograph - one is certainly more prominent).

Unfortunately we didn't see it in flower, but the pale yellow heads stick out from a dangling stem, presumably a few weeks before we arrived to find the seed.

Tuesday, 24 January 2017

Popping out to see the upside down orchid

This is what we awoke to yesterday, the 23rd of January. A 15 cm wide, fleshy, orchid flower emerging from a basket brimming with pseudobulbs (the swollen bits at the base of the aspidistra-like leaves). It's a Stanhopea, induced into flower by either Lynda fertilising it last week or a liking for the recent warm and (particularly if we keep the water up) humid weather.

Species of this genus are sometimes called Upside Down Orchids, referring to the propensity for the flowering stem to head downwards, or slightly misleadingly Bucket Orchids, a name more often applied to the related genus Coryanthes which does have a 'bucket' as part of its floral apparatus.

We first noticed buds on Saturday afternoon (21 January), exactly one year after friends Maggie and Max Richards gave us half of their Stanhopea basket plant. We were to look after it, and try and get it to flower. Job done!

That said, it hasn't looked great for most of the time, with leaves a bit tattered and browned. We moved house in April, meaning its microhabitat changed from subtropical Hawthorn to subtropical Glen Iris, so that may not have helped. Typically it prefers the subtropics of more northern parts of Australia I suspect. Still, in its final resting place under this nectarine tree it seems happy enough. At least happy enough to flower.

The flower buds had presumably been there a day or two, or even more. After Lynda spotted the first two we noticed a younger second pair at the back of the basket. The two at the front though (below, photographed 21 January) looked like juicy, slightly deformed, capsicums, and ready to open any day...

It all happens quickly with Stanhopea so we kept vigil over the next few days. I had heard that their flowers audibly 'pop' open and it seems that mostly the popping occurs early in the morning: 5.30 am according to most reports or, if you are lucky, as late at 8.30 am.

I didn't hear a pop but at 6.00 am on 23 January this is what our flowers looked like - one open, one still shy. The open flowers are like porcelain, or plastic, depending on how much romance you want to evoke. The chunky insides must be like a theme-park ride for any willing pollinator.

In nature the flowers are pollinated in nature by a male (euglossine, or orchid) bee which visits the flower to collect aromatic substances from the waxy lips of the flower. On the way in, or out, it collects some of the orchid pollen to then carry to another flower.

And aromatic the flowers are. On the morning this flower opened there was a strong waft of a vanilla-like fragrance curling around my nose as I photographed what a male bee sees (in different colours) and experiences. In this bee-view picture, the pollen sits in a small notch behind that small pointy bit that seems to make the entrance to the ride unsafe.

It's fitting to seek information on this species from Royal Botanic Gardens Kew. Stanhopea was named by Sir William Hooker, an early Director of Kew, for a genus of orchids found mostly in tropical Central and South America.

There are now over 60 species known and I think ours is Stanhopea tigrina* (Tiger-spotted Stanhopea), from Mexico, perhaps the mostly commonly grown species of Stanhopea in Australia.

Stanhopea nigroviolacea is another name you'll see around for a plant with similar looking flowers. That species was in fact named originally as a variety of Stanhopea tigrina, and in the most recent version of Plant List you'll find Stanhopea tigrina var. nigroviolacea. 'Nigroviolacea' seems to have more of the maroon colour on the floral parts than mine but I'm happy to be corrected on this (now infraspecific) identification!

Stanhopea tigrina was named and described in 1837 by James Bateman, the author of a rather large (10 volume) publication on the orchids of Mexico and Guatemala. By the time this hand-coloured lithograph by W.H. Fitch appeared in Curtis’s Botanical Magazine, in 1845, the species was 'not uncommon' in the collections of UK plant enthusiasts.

You can find Stanhopea in cultivation around Australia, in the collections of orchid buffs mostly, but not too many in Melbourne; we grow it inside our Tropical Glasshouse in the Melbourne Gardens of Royal Botanic Gardens Victoria. Our home display is modest when you see some of the pictures on the web of the underside of baskets lined with flowers, but even one of these flowers is marvel enough.

When I got home last night the second flower in the pair was open. Apparently, Lynda says, it was open at 8.30 am, when she ventured into the Gardens. So maybe one at 5.30 or thereabouts, and the other closer to 8.30, just like the interweb said.

Thank you to the Richards family for a gift that took a year to deliver, but deliver it did.
*Sydney-based expert on exotic and local orchids (among other things), David Banks (via Facebook, 27 February 2017, when I reported another set of two flowers opening), says my plant is definitely Stanhopea nigroviolacea, and not Stanhopea tigrina. He posted a picture of a different looking flower, identified as Stanhopea tigrina, by Barney Greer "who wrote a book on this genus".

Tuesday, 17 January 2017

Pretty, leafless, and not a guinea worth

The genus name Hibbertia honors George Hibbert, a lover of plants and patron of botany. George was a fellow of the Royal Society and the Linnean Society in London, and purchased collections of preserved plants (herbaria) as well as funding collecting trips to, for example, the Cape of Good Hope in southern Africa.

If we look at this particular species (Hibbertia dilatata, above) from the Top End of Australia and compare it to those more usually associated with the name George Hibbert, you'd be looking for leaves and perhaps more yellowish flowers. The one below is your more 'typical' Guinea Flower, from Ku-ring-gai National Park.

And this one from our front yard, Hibbertia stellaris, a native to Western Australia, stretches the yellow to orange, but at least it has leaves.

There are around 250 species of Hibbertia in the world, the vast majority found in Australia but with some in Madagascar, New Guinea, New Caledonia and Fiji. Northern Territory has 50 species, with 28 of these added as new in 2010 (by Helmut Toelken) and five moved across from what used to be called Pachynema, a mostly leafless groups of plants.

Flowers of the genus Hibbertia can be yellow, orange, pink, white or red, but many species do have yellow flowers - hence the common name, Guinea Flower. The flower from the Northern Territory has white to creamish petals, but more often flushed with pink. This flower has three remaining of the five petals. Still pretty, but not conjuring up a guinea.

Pachynema means thick filaments. Filaments are the stalks that hold the sacks of pollen aloft in a flower, and these flowers have ring of stumpy bottle-like filaments just inside the petals, as you can see here (in yellow).

Like other species previously called Pachynema, Hibbertia dilatata has no leaves - although some species in that group have leaves only at the very base of the plant. The stems of such plants are photosynthetic (green) and usually flattened. In this case, very much flattened and looking like a long strap-like leaf.

As a gratuitous aside, this particular specimen was growing in a recently burnt area near Greenant Creek, in Litchfield National Park. The ants in question were nesting in the leaves of a nearby Red Paperbark (Lophostemon lactifluus); illustrated, with ants, below. You can bite their green bums off for a tangy treat.