Fruiting karaka

Karaka (Corynocarpus laevigatus) is a small New Zealand tree with large fleshy fruits.  It's interesting for a number of reasons.  Its fruits were an important food resource for Māori but the kernels had to be treated to remove the toxins they contain.  It's become a weed in some parts of the world. Some botanists consider it a weed within New Zealand too, when it becomes invasive outside its presumed native range or habitats.

Right now, karaka trees are fruiting heavily.  But not all of them.  Some trees are covered in fruit and others have none or very few.  Some years ago, I wondered if this meant they had separate sexes, and was able to show that this is the explanation (Garnock-Jones et al. 2007).  Male trees do produce a few fruits, so the sexual system in karaka is best described as gynodioecy (some plants strictly female; others are inconstant males).

Here are the two trees that started this research off, photographed this month in Kelburn.

Karaka trees in fruit, Kelburn, Wellington, 2014

Here are the same two trees about 10 years ago.

Karaka trees in fruit, Kelburn, Wellington, 1998 (from Garnock-Jones et al., 2007)

On the female tree, the panicles fruit heavily, with many of the flowers (but by no means all) developing fruits.

Fruits on a female karaka tree

On males, usually a single fruit develops on each of a few panicles.

Fruits on a male karaka tree

Karaka flowers are small and white, but if you look closely you can tell the male from the female flowers.  The male flowers are actually about twice the diameter of females, open more widely, and have pollen in their anthers.  The male flowers in the photo have pollen on the stigmas, but only very few of them will produce fruits.

Karaka flowers.  On a female tree (left); male tree (right)

Reference.

Garnock-Jones PJ, Brockie RE, FitzJohn RG 2007.  Gynodioecy, sexual dimorphism and erratic fruiting in Corynocarpus laevigatus (Corynocarpaceae).  Australian Journal of Botany 55: 803–808.

Wednesday Wildflower: tarweed

Tarweed is flowering at the moment.  Parentucellia viscosa is an erect herb with small yellow flowers and its leaves are covered with glandular hairs so dense they feel sticky to the touch.  You'll see it in damp patches beside roads and tracks, along the edges of ditches, and wet hollows in grassland.

Tarweed, Parentucellia viscosa, Karori, Wellington

It's a hemiparasite, which means it derives some of its nutrients parasitically from other plants, but it's also green and able to generate its own energy through photosynthesis.  Full parasites (holoparasites) usually lose the ability to photosynthesise and to make green pigments, so they are often brown or pale.

Tarweed flower.

It's related to Euphrasia, another genus of hemiparasites, of which we have a large number of native species in New Zealand, and to the introduced broomrape, Orobanche, which are holoparasites.

Orobanche minor, broomrape, near Nelson.

The hemiparasites Parentucellia and Euphrasia used to be classified along with Veronica in the family Scrophulariaceae, but it was discovered a decade or so ago ago that Scrophulariaceae as it was then drawn up wasn't a natural group (of related plants).  So that previously large family has been split up. Veronica was transferred to be classified with its relative Plantago (Plantaginaceae), and Parentucellia and Euphrasia joined their relatives the broomrapes in Orobanchaceae.

Ngaio, Myoporum laetum, Wellington

Although Scrophulariaceae has been dismembered into 7–10 different families to make a more natural classification, it still exists as a much smaller family, many of them African.  Our only native member is Myoporum, ngaio.

The Great Veronica Hunt —Part 6.

I'm writing this in Melbourne, where I'm about to fly home after a wonderful three weeks in Australia. I wasn't specifically on a Veronica hunt, but kept my eyes open anyway, just in case.

I didn't see any Veronica in Queensland or around Sydney. The first I saw was the introduced V. arvensis in Bega, a small New South Wales town.  Australia has many of the same weedy speedwells that New Zealand does, so I was more interested to see plants of the indigenous species.

Mallacoota inlet, Vic.

We spent a couple of days with friends at Mallacoota in the far east of Victoria, and there came across V. plebeia growing beside a track in coastal forest in the wonderfully-named Croajingalong National Park.

Veronica plebeia, Mallacoota, Vic.

The flowers were closed just as they often are in New Zealand, needing a warm sunny day to open.  If they don't get to open, I assume they self-pollinate, because they always seem to set fruits.

The flower below was photographed on a cultivated plant in New Zealand, where V. plebeia is widespread and considered by some botanists to be native.  It is introduced and weedy in some other parts of the world though, so it does have the ability to be invasive.

Veronica plebeia, from a cultivated plant in New Zealand.

That was it for wild speedwells the whole trip, but my sister-in-law, near Ballarat, had some small plants of another Australian native, Veronica gracilis, ready to plant out in the garden, and one of these was in flower.

Veronica gracilis, cultivated near Ballarat, Vic.

The plants are strongly rhizomatous, and this one even had a shoot coming out of the drainage hole in the bottom of its pot.

Australia has 23 native species of Veronica, classified in section Labiatoides, and they are the sister group to the large New Zealand clade (section Hebe) that includes the hebes and their relatives (Albach & Briggs 2012).  Thus, although they look much more like northern speedwells than New Zealand hebes, they are known to be more closely related to the hebes.  And because of that fact, it's misleading to classify them as Veronica unless you classify our hebes in Veronica as well.

Reference

Albach, D; Briggs, BG. 2012. Phylogenetic analysis of Australian species of Veronica (V. section Labiatoides; Plantaginaceae). Australian Systematic Botany, 2012, 25, 353–363
http://dx.doi.org/10.1071/SB12014

The Great Veronica Hunt — part 5.

(Note: I've updated this post on 28 September, giving the name of the botanist whose advice led me to these two Veronicas and whose collections in New Zealand herbaria verify those discoveries.  The changes are underlined.)
 
If you've been paying attention, and I'm sure you have, you'll notice I haven't posted the Great Veronica Hunt part 4, but that's what I should have called this post a couple of weeks ago.  So, skipping part 4, here's part 5.

In part 1, I described trying to find Veronica peregrina last year.  That was frustrating, because although I had a very accurate description of the location and the habitat, I was there too late in the season. To make it worse, the original collector—Whanganui botanist Colin Ogle— hadn't seen it there for a few years and doubted it would still be present.  Still, Colin had told me last autumn of a site for another species I need to photograph, V. chamaedrys, so yesterday I went after them both.

Veronica peregrina plants, Kakariki.

It took a while to find V. peregrina, but it is still there.  It was growing in silty gravel at the edges of dried up puddles in a rough vehicle track.  The biggest plants were about 75 mm tall, and the small white flowers weren't fully open on a rather dull day.  I brought some plants back to photograph, some to grow, and some to make a couple of herbarium specimens.

Veronica peregrina

This is an American plant, and it seems to be often associated with railways in the States, so it's interesting that this site is right beside the main trunk railway, at Kakariki, near Marton.  I don't know whether the activities of railways spread seeds around or whether they create suitable habitats, or maybe it's just a coincidence.

V. peregrina plants are bright green and either have no hairs or very few long glandular ones.  Their flowers are pure white, an unusual colour for a northern hemisphere Veronica (most are blue), but a common colour among our native species (only a few of which are blue).

While at Kakariki, I'd promised a colleague I'd look for spore-bearing cones on Equisetum arvense, which is naturalised along the banks of the Rangitikei River.  I'd seen it there in abundance last trip, so I confidently went down to the river.  However the river banks have been extensively sprayed, and, while it hasn't completely cleared the infestation, it's knocked it back pretty severely.  Eventually I managed to find a single cone, and took photographs and a specimen.

Equisetum arvense

Equisetum (horsetail) is an odd plant, now known to belong among the ferns. The cones produce not seeds, but spores (pine cones produce spores too: male cones make male spores that develop into multicellular pollen grains before they're dispersed, and in the familiar female cones the spores are retained, develop there, and after fertilisation each develops into parts of a seed).  Horsetail spores are formed in cylindrical sporangia underneath the hexagonal umbrella-like scales on the cone, which spread apart to release them.

Equisetum arvense, spore-bearing cone.

Then it was on to Marton for lunch and through Whanganui to the hill country inland from Kaiiwi. Colin Ogle had told me of a locality for Veronica chamaedrys, a plant I'd seen and photographed in England and France, but one that's naturalised in a few scattered localities in New Zealand.

Veronica chamaedrys,  St. Léon sur Vézère, Dordogne, France.

Here in the bush it grows around the edges of a small clearing in an old waterworks reserve.  How it got here is anyone's guess, but it's well-established in a small area.  We were too early for flowers, but it's a vigorous plant and I'm sure we can grow it on at home in a semi-shaded spot.  If this works, I'll post photos later.

Veronica chamaedrys at the edge of the clearing

The roadside cliffs through the bush were covered in flowering plants of Ourisia macrophylla subsp. macrophylla, and some of them were pink-flowered, at least in the bud.  I'd never seen such colour in New Zealand Ourisia, but in South America there are both red- and pink-flowered members of this genus.

Pink Ourisia.

It's always odd going back to Whanganui.  That's where we first settled when we emigrated to New Zealand in 1955.  I started school there (this is me on the left end of the middle row), and we used to swim at Kaiiwi Beach.

Wednesday wildflower: Veronica hederifolia

Last week I was at Lincoln, near Christchurch, working in the herbarium at Landcare Research.  I was checking my descriptions and identifying specimens towards my Veronica treatment for the new on line Flora of New Zealand, the eFlora.

Veronica hederifolia growing at the foot of an oak tree in the Liffey Domain, Lincoln.

One of the introduced species (there are about 20 of them) that I hadn't yet seen grows right there in Lincoln, so it seemed a good opportunity for a field trip to collect and photograph it.  Veronica hederifolia plants are soft annual herbs that creep along the ground.  Their flowers appear to be solitary in the axils of the upper leaves, but that depends on an interpretation.  Leaves that don't produce flowers are opposite, but there's a shift to alternate leaves, each of which has a flower in its axil.  It's probably reasonable as an alternative interpretation to consider this to be the initiation of a terminal inflorescence. In any case the leaf form doesn't change, whereas in many Veronica the flowers are produced in the axils of much smaller and simpler leaves, which are designated as bracts.

Veronica hederifolia growth form.

V. hederifolia has been growing there in Lincoln along the banks of the L2 river for over 50 years.  The botanist who collected it last—in 1985—was able to tell me exactly where to look, and there it was. There's one other collection in Landcare's herbarium, from St Mary's College grounds in Christchurch, and the Flora refers to other verified locations in Hawke's Bay, Manawatu, and Southland.

Although V. hederifolia looks a bit like V. persica in the way it grows, there are a lot of clear differences.  The leaf shape for one, but also the flowers are smaller, and the anthers are held right against the stigma so it self-pollinates, in spite of producing lots of nectar.  The fruits of V. hederifolia are hairless, circular, and barely notched, whereas fruits of V. persica are hairy along the edges of two widely diverging lobes.

Veronica hederifolia flower.

The calyx lobes are folded length-wise and have long hairs along their edges.

Veronica hederifolia, calyx.

I've taken a few small plants to try to grow it on at home, but annuals can be hard to transplant, so I'm hoping fruits and seeds will be ready when I go back to Lincoln next month.  Then I'll be able to finish my description by describing fruits and seeds and bring home some seeds to grow in the garden.

Wednesday wildflower: old man's beard.

“Old man’s beard must go,” said the not-so-young bearded botanist David Bellamy some years ago on TV, and we all knew this was a serious weed that threatened to smother our native forests.  Since then, it’s not as common as it used to be.  The efforts of the Department of Conservation, local and regional councils, community groups, and individual landowners have largely seen off the worst infestations in many places.  But around Wellington city, and probably many other places, there are little pockets of old man’s beard everywhere.  My guess is it’s waiting for our vigilance to let up and it’ll be back with a vengeance.

Old man's beard fruits, Northland, Wellington.

Old man’s beard is called traveller’s joy in England, which goes to show that one country’s wildflower is often another’s weed.  The local name refers to the fluffy white plumes on the seeds.  More accurately (with my pedantic botanist’s hat on) these aren’t seeds but fruits, each bearing a single seed inside a loose-fitting fruit wall.  The flower, like many in the buttercup family, has multiple separate pistils, each with its own ovary, style and stigma.  After pollination, the pistils from a flower mature into a cluster of separate 1-seeded fruits, each with the fluffy remains of the style to form a plume that assists in wind dispersal.

One of the practical problems with a public eradication campaign is that people need to be able to recognise the target weed, and not try to eradicate look-alikes.  Many people worry that they might be pulling up one of the native Clematis instead, so I thought this week a few notes about these plants might be useful.

First, old man’s beard (Clematis vitalba) is one of just two species in New Zealand with once-pinnate leaves; they have a central axis with a terminal leaflet and two pairs of lateral leaflets.  The other species that’s characterised by once-pinnate leaves is C. maximowiciana, but its leaves are more leathery than the leaves of old man’s beard; also it has larger flowers, 30–50 mm diameter.  Most of the other species have three leaflets although these can be quite finely divided.  Two species, C. tangutica (yellow flowers) and C. flammula (white flowers), have twice-pinnate leaves (the pinnae [leaflets] are themselves pinnately divided).  The native C. afoliata has no leaves at all, just the leaf stalks that twine around supporting shrubs’ stems.

Old man's beard flowers, Kakariki, Manawatu.  They are mostly 12–25 mm diameter

Secondly, the introduced species mostly have 4 sepals in each flower, but many (not all) of the native ones have six.  All the introduced Clematis have hermaphrodite flowers (with functional stamens and pistils) whereas the natives all have unisexual flowers on separate plants (flowers have either stamens or pistils, but never both).

Clematis forsteri, a native species.  Pale yellow male flowers with 6 sepals.  If you see these, don't just look, sniff too: many are sweetly scented.

Most of the native Clematis flower in the springtime or even late winter (some plants of C. forsteri are in flower now in late July).  Old man’s beard is a summer-flowering plant, mostly from December to May.

Clematis paniculata, another native species, male flowers.

Old man's beard flowers are greenish white.  Most natives have pale or greenish yellow flowers, although the large (and unisexual) flowers of C. paniculata are pure white, C. marata and C. marmoraria are white or greenish, and C. marata quadribracteolata (corrected 4 September 2013) brown or purplish brown.  Finally, the introduced Clematis are all deciduous whereas the natives are all evergreen (except poor C. afoliata, which hasn’t got leaves to lose).

Old man's beard still must go, but let's hope no native Clematis get pulled out instead by well-meaning weed-busters.  The Flora treatment for their identification is on line at Landcare Research's website and you can find pictures identified by botanists at the Naturewatch site..

Wednesday wildflower: winter heliotrope

Winter heliotrope isn't a true heliotrope, but a daisy, related to the senecios I've featured in a few other entries in this series (here and here).  But it is both a wildflower and a weed, a garden plant that has escaped.

Winter heliotrope, Petasites fragrans.

This patch was in Aro Valley, an old-established part of Wellington, originally working class but now a mix of gentrified old cottages and student flats, arty cafes and boutiques.  The plants were in a garden that had a rather wild appearance; I'm sure its owner was deliberately aiming for a wilderness look.

Winter heliotrope flower heads.

The flowers are pink, instead of the usual yellow for this tribe of daisies (Tribe Senecioneae, characterised by the involucral bracts being in a single row, not in overlapping rows like roof shingles).  Winter heliotrope is dioecious (has separate male and female plants), but all the plants in New Zealand are males.  Their outer ray florets are all sterile (they make neither pollen nor seeds); ray florets are female in most daisies (the general structure of daisy flower heads is explained here).  The inner disk florets are male (often hermaphrodite in other daisies).  Not being able to have sex doesn't deter this plant a bit, because it is able to spread vegetatively, and of course people deliberately and inadvertently help that process.

You might note the stigmas in these florets, the large white somewhat feathery things poking through the tube of purple anthers in the centre of these florets.  How come male florets have such a large stigma?  In this and several other families, the pollen is presented on the stigma, so even though the florets are male, they still need well-developed female parts for pollen dissemination.  In a hermaphrodite daisy floret, the stigma opens after the pollen has gone to expose the two receptive surfaces.  I didn't examine these closely at the time, but in the photo I can't see any that have opened.

Wednesday wildflower: Red carpet, brown carpet

When I use the term wildflower, it's often to avoid the judgmental term "weed".  I like most plants, and if other people have species they don't like, well, that doesn't necessarily stop me enjoying them.  Furthermore, plants we designate as weeds are often biologically very interesting.  To a botanist, the term "weediness" has an ecological meaning that signifies more than a nuisance plant.

Pōhutukawa flowers

One of the interesting things weeds do well is reproduce.  All that any plant or animal needs to do is to reproduce itself at least once, but because an outcrossing sexual plant or animal contributes only one of its two sets of genes to each offspring it must do it twice to break even.  Even then, reproducing a few times doesn't guarantee the survival of all your genetic material, because which copies of genes get into a sperm or egg is random.  But some plants seem to reproduce in overdrive.

Weeds often succeed because they out-reproduce other plants.  Some are long-lived and may spread vegetatively, but others produce huge numbers of seeds.

A few red stamens have accumulated in the gutter beneath these trees, but sometimes, if it's not windy, a thick red carpet can build up.

Today's wildflower is a weed in the biological sense, but to New Zealanders it's a much-loved native flowering tree, the pōhutukawa, Metrosideros excelsa.  Pōhutukawa puts a lot of effort into reproduction, and that's probably why it's an unwanted weed in some other parts of the world where it has been introduced as an ornamental, like South Africa and Hawai'i.  Some people also consider it a weed in parts of New Zealand that are outside of its native range, such as Wellington, because it's invasive and aggressive there too.

A cluster of pōhutukawa flowers; each individual flower has about 25 red stamens (with yellow anthers) and one red style.

Pōhutukawa reproduction seems wasteful.  The trees flower profusely around Christmas time in New Zealand and in the later part of each flower's life the bright red stamens fall to the ground where they can form a thick red carpet.  This isn't over-production particularly; it's just that the red stamens are so visible and there are so many flowers producing them.  They can be dispensed with once their pollen has been dispersed.  They're visible for a good reason: pōhutukawa is primarily pollinated by birds (tūī, bellbirds, but also silvereyes and starlings) and the red colour attracts them because birds see well in the red wavelengths.

A bit later in the summer, many of the old flowers themselves fall.  I guess these are flowers that aren't setting seed; they no longer have a function and the plant can discard them.  I don't know whether these are functionally male flowers or simply flowers that didn't get pollinated, but these form a pale grey-green carpet for a time.

Pōhutukawa seeds in the gutter, Kelburn, Wellington

The third big dump of reproductive material is happening about now in Wellington, and that's the dispersal of seeds in their millions.  Most of these are never going to germinate.  They pile up in gutters, on footpaths, and at the bases of walls.  I'd like to do a rough calculation of the weight of stamens, aborted flowers, and seeds produced by a large pōhutukawa tree in a season; I think we'd all be surprised.  Multiply that, whatever it is, by the number of trees in Wellington and that's a lot of biomass falling to the ground each year.

Pōhutukawa seeds.

This prodigious reproductive effort is one of the attributes that makes pōhutukawa such a successful plant, and it's a trait normally associated with weediness.  No wonder then that our Christmas tree has become a pest in places.

Improvised macro lens for a point & shoot camera.

Flower of an unnamed native buttercup, photographed with my old Spotmatic. The flower is probably about 15 mm diameter.

Years ago (about 1970) I was given an Asahi Pentax Spotmatic 35mm camera with a 50mm macro lens.  I used that camera for field and family photography for about 30 years.  It was tough and I never had it serviced, and sometimes the photos were great.  In the last 12 years I've had three different digital cameras, all cheap(ish) point-and-shoot models.  While they get pretty close, they don't match the best performance of the Spotmatic for plant close-ups, although they have some real advantages.  On the whole I'm pretty happy with the latest one, a Sony Cybershot 14.1 megapixel camera.  It's small and light and has a macro function that does a reasonable job with all but the smallest flowers.
 
Digital cameras are evolving rapidly and so I seem to need a replacement every few years. Fortunately they're also getting cheaper as they get better.  I'm reluctant to shell out a lot of money for a digital SLR, knowing in a few years it'll be obsolete, or at least surpassed by newer models.  However, I would like to get closer to small flowers, so I've been playing with cheap alternatives.

The latest is a $10 home-made macro lens.  It's inspired by the idea of the Ōlloclip lenses for iPhone (I've just bought a set of these and they're pretty good and very portable).  You can get reasonable results by simply holding a botanist's field lens in front of the camera lens, but I was lucky enough to have a cheap jeweler's loop that fits quite snugly over the lens of my camera.  Unfortunately though, it's a bit tricky to hold it aligned in place while you take the photo.  I wanted something a bit more stable.

I hit on the idea of using cheap plastic plumbing attachments to hold the lenses together.  Here's the camera with the parts of the new system.  The loop fits snugly in one end, and the other end fits snugly over the camera lens when it's extended.  You have to zoom a bit to fill the field of view.

My point & shoot camera with components of the clip-on macro lens: a $2.50 plastic pipe attachment and a $10 jeweler's loop.

And here's my camera with its new macro lens fitted.  I still have to hold it while I take the photo, but the pipe fits snugly so I don't have to position it as well.  I could superglue a threaded plastic ring onto the camera, then screw the pipe attachment into it (it's threaded on both ends), but I don't want to do that to my camera, at least until it's out of warranty (in a few weeks).  If I did that, I could put the camera on a tripod for greater stability and better focusing, so I might do it quite soon.

The macro lens clip-on in place.

The real test is in the results.  Here are three shots for comparison: using the standard camera as close as it can get (left), then using the new clip-on lens with the zoom half-extended (centre) and fully extended (although not quite focused, right).  Printed at 300 dpi, the 1 cm wide key in the right hand picture would be about 33 cm across:

The new system has quite a good working distance and is easy to use.  There is a little distortion of parallel lines (see above), and there might be other effects like chromatic aberration that I haven't looked for.  But at $12.50, it's a bargain.  I'm playing with other improvised systems too, and might report on them later.

I used it in the field this week too:

Veronica scutellata, Foxton Beach.  In the original photo, the flower was 1240 pixels across; in life it's about 6mm.

Veronica catenata, Himitangi Beach.  In the original photo, the flower was 800 pixels across; in life it's about 4 mm.

To finish, here's what the Ōlloclip macro lens can do with an iPhone 4S:

Veronica serpyllifolia capsule.  It's 4 mm across, and spans about 600 pixels in the original.

It focuses at 13mm, so I guess I need some kind of adjustable stand to hold the phone at that distance from the subject.  I've started building one.

Wednesday wildflower: moth plant

Moth plant isn't something I've noticed before, but this week I'm holidaying on Waiheke Island and seeing quite a few northern weeds.  Moth plant, Araujia sericifera, is one of these.

It's a twining climber that smothers shrubs and trees.  Moth plant was introduced probably as an ornamental, but like many it has escaped to become an environmental nuisance.  It's native to South America, although might have been introduced here from Europe, where it is cultivated.

The quite large (about 20-25 mm diameter) fragrant flowers are pollinated by moths, among other things.  It's also known as "cruel plant", seemingly because the petals close around pollinating moths at night and release them in the morning.

Parsonsia heterophylla flowers.  Scale = 5mm.

Our only native member of its family, Apocynaceae, is Parsonsia, with three species.

Strange violets.

Māhoe (Melicytus ramiflorus) is one of the plants I love to show to visiting botanists from temperate Europe or North America.  They invariably ask, "What family is it?" and the answer always surprises because they're used to Viola as the representative of Violaceae.  Here's a violet that's a tree, has radially symmetrical flowers, and fleshy fruit; the world truly is upside-down in New Zealand.

Māhoe flowers on twigs of a male tree, Karori, Wellington

Well, not so fast.  It's true Viola is the type genus of Violaceae, but who said types have to be typical?  The type simply determines the application of the name according to the rules of nomenclature.  It's the circumscription—the definition of the membership of the group—that outlines its overall collective characteristics.  Violaceae is a largely tropical family, and they're woody except for Viola.  Quite a few have radially symmetrical flowers and fleshy fruits (Mabberley 2008).

A "normal" violet (Viola sp.), France.

Māhoe might be New Zealand's commonest tree.  There's certainly lots of it around Wellington, where it's an important component of the still low second growth forests that, over the last 50 years, have replaced the gorse on hills around the city.

Māhoe flowers in pulses, all the trees in a location flowering in synchrony several times a summer (Powlesland et al. 1985).  Coffee does the same thing.  The flowers are small and borne on the twigs, a form of flower presentation called ramiflory.  They're scented, especially at night, but it's not a very pleasant smell, in my opinion.

Melicytus ramiflorus, male flower.  Note the vestigial ovary in the centre and the swollen connective at the back of each anther that functions as a nectary

Melicytus ramiflorus female flower.  Note the large stigma and the nectar produced from the connective at the back of each staminode.  Female flowers are about 2/3 the size of males.

The flowers are unisexual and produced on separate trees, so a whole tree is either male or female.  The connective of the stamens and (in female flowers) staminodes is also the nectary, and each produces a glistening drop as a reward for the pollinators.

Māhoe leaf skeletons

Their leaf veins are pretty tough, but the rest of the leaf decomposes freely, to leave exquisite lacy leaf skeletons on the forest floor.

Viola cunninghamii, Hooker Valley, Mt Cook National Park.

New Zealand has three native violets (like V. cunninghamii above), plus some introduced species.  We also have quite a few Melicytus; some are small trees and others are twiggy shrubs.  Some used to be classified in the genus Hymenanthera, but that was merged with Melicytus in the 1980s.  Recent research (Mitchell et al. 2009) shows there are two pretty clear-cut groups within the genus, although the authors didn't draw attention to it, and it might make sense to recognise Hymenanthera again.

References

Mabberley, D.J. 2008.  Mabberley's Plant-Book (3rd ed.).  Cambridge.

Mitchell, A.D.; Heenan, P.B.; Murray, B.G.; Molloy, B.P.J., de Lange, P.J. 2009.  Evolution of the south-western Pacific genus Melicytus (Violaceae): evidence from DNA sequence data, cytology and sex expression.  Australian Systematic Botany 22(3) 143–157.

Powlesland, M.H.; Philipp, M.; Lloyd, D.G. 1985.  Flowering and fruiting patterns of three species of Melicytus (Violaceae) in New Zealand. New Zealand Journal of Botany 23: 581–596