Tuesday, 25 December 2012

Wednesday wildflower: centaury

Plants classified in the gentian family, Gentianaceae, have mostly radially symmetrical flowers, so when I looked closely at this common pink-flowered weed I got a bit of a surprise.  Its calyx and corolla are indeed radially symmetrical, but the stamens and style curve away to opposite sides of the flower, keeping out of each other's way.
Centaurium erythraea, Karori, New Zealand.
It shows nicely in a photo on this blog from Spain too, and in this case the flower colour is more intense.  The stigma is two-lobed, and the five stamens are bent away from it.

This separation of male and female parts in a flower is called herkogamy.  There are different kinds of herkogamy, classified according to how they function.  This looks a bit like movement herkogamy, where one sex is presented first, then moved away to make room for the other sex.  Here you might imagine that the stamens were presented in the middle of the flower, then moved to one side as the stigma grew up.  However, all the flowers I saw—young ones and old ones—were like this, so it clearly doesn't change as the flower ages.  It could be approach herkogamy, which ensures a pollinator contacts one sex first, except that a radially symmetrical flower like this can be approached from any direction.  It'll need some observations of how pollinators interact with these flowers, and that's best done in its native range, in Europe.
Gentianella, Enderby Island.
New Zealand has many native gentians, mostly white-flowered.  They're classified in the genus Gentianella.  On the subantarctic islands, flower colour is very variable, from white through to deep red.

Addendum (27 December 2012)

In Europe, centaury is pollinated by hover-flies, with a fail-safe mechanism for delayed self-pollination in the event of pollination failure (link here).

Thursday, 20 December 2012

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.


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

Monday, 17 December 2012

Sun orchids

I haven't paid a lot of attention to orchids; I've been focused on other plant groups.  But I could get keen on them now, after having a look at some this week.

When I was a young lad, my Dad learned in a conversation at work that New Zealand had "a rare native orchid", and I imagined I'd never be lucky enough to see it.  Not long after, I lost my footing in what we called "the bush" (now the Wilf Mexted Reserve at Tawa), and when I'd slid to the bottom of the bank I looked at the vegetation in my hand that I'd grabbed to slow my fall.  There it was, the rare native orchid!  I'd pulled it out of the ground, maybe it was the last one.

I was too ashamed to tell anyone, until much later.  When I got to University, I found that my orchid was the common greenhood orchid, Pterostylis banksii, and that there wasn't just one species of native orchid, but lots.  Some of them are indeed rare, but many are common.  They're all interesting, in part for the exquisite shapes of their flowers and the complexity of some pollination arrangements.

Thelymitra longifolia on a bank in Karori, Wellington.
This is another of the common ones, a sun orchid, Thelymitra longifolia. Its flowers are usually white, but sometimes pink, and some people suspect there might be several species going under the one name. The bits and bobs attached to the central column are distinctive, and useful in telling if you have this or one of the other species of Thelymitra.

Thelymitra longifolia flower.
The outer parts of the flower comprise three sepals and three petals.  In most orchids the petal in the front of the flower is highly modified as the labellum (e.g., the slipper in slipper orchids), but in sun orchids all three petals are alike so the flower is quite symmetrical.  In the middle of an orchid flower, the central column combines the male and female organs.

Thelymitra longifolia, side view (left) and front view of column.
There's a single stamen and a sticky stigma, and a whole lot of other features (terminology follows Moore & Edgar 1970).  The column surrounds the stamen and stigma on three sides and extends into a hood at the top, furnished with two column arms, each with a tuft of white hairs.  Behind the stamen is a pointed post-anther lobe; you can faintly see the sides of it above, but its tip is hidden behind the hair tufts on the column arms.  The glistening knob between the anther and the stigma is the rostellum, and it's believed to be a modified lobe of the stigma.

Thelymitra longifolia is considered by some to be self-pollinating.  Charles Darwin quoted Mr Fitzgerald's Introduction to Australian Orchids that it's fertilized in the bud, although it does sometimes open enough for cross pollination to occur.  Part of the evidence for selfing is the pollen doesn't bind together into two cohesive masses, the pollinia, but the grains separate and scatter about the inside of the hood, many apparently landing on the stigma.  Also the flowers often stay closed; they only open briefly on the sunniest of days.  But if self-pollination's the whole story, then it's hard to understand why the column is so complex and how the pollen gets to the stigma without some disturbance.  In the first flower I photographed there was a thrips, a tiny pollen-feeding insect that some people believe are important pollinators.  He was head down-bum up in the anther, spilling pollen around, but none had reached the stigma.
Thelymitra venosa, here on Stewart Island, is brightly coloured and has a relatively enlarged labellum.  It's more likely to be insect pollinated.
The onion-leafed orchid, Microtis unifolia.
I photographed another orchid this week.  This one, Microtis unifolia, comes up wild in the plant pots at home.  They each have a single leaf, and a stalk of tiny green flowers, each just 3–4 millimetres across.
Microtis unifolia, note the labellum hanging down at the front of the flower.


Darwin, C. 1862.  The various contrivances by which orchids are fertilised by insects.  Murray, London. (I have the 1904 edition.)

Moore, L.B.; Edgar, E. 1970.  Flora of New Zealand. Vol. 2.  Government Printer, Wellington.

Saturday, 1 December 2012

Bring the Aurora back to Wellington.

Wellington Harbour, from Johnson's Hill.
Wellington City curves in a gentle arc around its waterfront, a vast public playground that's the envy of many other cities.  Because of its almost land-locked harbour and its position on the southern tip of the North Island, Wellington has always been a maritime city and I think it always will be.

Sculptures make the waterfront an attractive and engaging place, but imagine a tall ship here!
On any fine day, the waterfront is thronged with walkers, runners, cyclists, skaters, rowers, fishers, swimmers, diners, and sightseers, all enjoying the cafes, museums, sculptures, wildlife, and the shipping.  But it doesn't have two facilities that many other waterfront cities enjoy: an aquarium and a tall ship.
Insert tall ship here.
Others have been busy working towards an aquarium, and although it looks like it's not going to happen on the waterfront it is happening.  But for a while now I've been musing about a tall ship for Wellington.  I don't have the personality or the connections to drive such a project, but after a few years of dreaming about this, I thought the least I could do was to write a blog post and put the idea out there.

Tall ships visit here from time to time of course, and in the old days the harbour was full of them (above).  In recent years the Spirit of New Zealand and the Spirit of Adventure have been occasional visitors, and the replica Endeavour and several naval training ships have paid us a call, to great public interest and enthusiasm.  Now I think it's time the capital city had a tall ship of its own.
The Endeavour replica in Wellington Harbour.
Our tall ship would be a link with our city's 19th century origins and would emphasize our maritime environment.  It'd be ideal to have a replica of one of our first immigrant ships, such as the Aurora.  The Aurora was a one of class of elegant ships called "Blackwall Frigates".  There are plans available for the class, if not for the Aurora itself.  Wouldn't it be an adventure to build it in New Zealand!
La Hogue, a Blackwall Frigate (The Illustrated London News', August 11th, 1855)
Our tall ship would be a tourist attraction.  It would add so much to the atmosphere of the waterfront, and it could be self-funding through cruises, much as tall ships are all over the world.  In my mind I can see it moored outside Te Papa.

Tall ships everywhere often double for youth leadership and confidence training.  That's a role Wellington could value too.  Sailing such a ship in Cook Strait has got to be character-building.  The Spirit of Adventure Trust has included Wellington youngsters on its cruises, but its ship Spirit of New Zealand is based in Auckland.

Last but not least, it'd simply be cool.

How much would a tall ship cost?

I've no doubt that building a replica Aurora would be an expensive proposition well into the tens of millions, but doing it would provide training and employment here in Wellington so a fair proportion of that cost would find its way back into our economy.  Buying an existing ship would be cheaper, although it wouldn't have the historical links with the city.  Look at this lovely steel brig for example: the asking price of 4.3 million euros would leave a little change out of NZ$7M.  That's not too bad.

Who would pay for it?

Personally, I don't believe it's the city council's role to bankroll items like this, but the council does support other projects, especially when they are tourist attractions or provide employment in the region.  Public subscription is another option, with different classes of donors promised something back: maybe a cruise if you give $2000, a free visit if you give $200 or pay an annual subscription to a trust.  There are probably groups in the city, service clubs and the like, who would willingly raise funds.  And corporate donations and sponsorship should be welcomed; at least one I can think of already has a close relationship with Wellington's winds.  Ideally, the ship would be self-supporting once purchased, but that might not be realistic.  There's plenty of experience around the world of running tall ships, and no doubt lots of enthusiastic people who'd be happy to help us get started.

So what do you think?  If you like the idea, pass it along by word of mouth and social media, comment below, or just click the "cool" box at the bottom of this article.  Let's get Wellington's wind in our sails!
Mast, top, shrouds, and yard.  Endeavour replica.

Friday, 23 November 2012

Tītoki and other New Zealand sexy plants

ResearchBlogging.org One of the peculiarities of New Zealand plants is the high proportion of them, among seed plants at least, that separate male and female sexual functions onto different plants.  Humans and most familiar animals do this too, so it seems to most people to be normal that there should be males and females in all organisms.  But most plants are cosexual; that is, there's only one kind of individual in a population, and it has both male and female reproductive functions.
Veronica decora (here at Moke Creek, Otago) is cosexual; every plant produces both pollen and ovules, in this case in hermaphrodite flowers.
In gender dimorphic plants—those that have two sexes—it's not always a straight-forward issue of being either male or female though.  When plants are either strictly male—producing pollen and no ovules—or strictly female—producing ovules but no pollen—the population is called dioecious.  But in many dimorphic plants, male individuals can also produce ovules and even set some fruits and seeds, a condition called gynodioecy.  Usually the males vary in their seed production, with most producing none or very few, and then a continuous range all the way up to a few plants that may produce quite a lot.  David Lloyd pioneered a method to quantify this variability in maleness and femaleness (it works for cosexual plants too), which helps greatly in visualising, describing, and ultimately understanding plant sexuality.
Female (left, cultivated) and male (right,  Makara Peak) of Aciphylla squarrosa.
New Zealand and a few other places, like Hawai'i, have a high percentage of species where there are separate male and female plants.  Maybe that's because genera like Aciphylla (above) and Coprosma, where all the species are separate-sexed, have undergone radiations here leading to large numbers of species.  But you can correct for that somewhat by using the genus as a measure: have we got more genera with separate sexes than other parts of the world do?

Colin Webb, David Lloyd, and Lynda Delph asked this question back in 1999 (free download here).  They calculated we have 83 seed-plant genera—23% of the genera in the flora—in which at least some species have separated sexes, and that's very high by international standards.  Since then a few more genera have been added to the list, like Teucridium, Toronia, and Corynocarpus (free downloads here, here, and here), but taxonomic changes have reduced the number a bit too, so the estimate is still probably about right.

Given this unusual feature of the flora, it's perhaps not surprising that New Zealand has produced a number of internationally recognised researchers of plant reproductive biology, headed of course by David Lloyd (1937–2006).  I've been aware for a while that nearly all of them did their research in the South Island, and we know that (roughly speaking) in New Zealand tree diversity decreases with increasing latitude, while alpine plant diversity increases.  So it's not surprising perhaps that the newly-discovered instances of separate-sexed genera are mostly northern and two are trees.  There might even be a few more waiting to be noticed; I've got my eye on another genus at the moment.

The variability of sexual systems in some genera, again often northern, still might not be fully described.  Kohekohe (Dysoxylum spectabile) and tītoki (Alectryon excelsus) were listed by Webb et al. as dioecious, but they need close examination to check for gynodioecy.  In kohekohe, a few fruits can be found on some male trees, and I've seen a few fruits on male tītoki, at least in cultivated trees.
Kohekohe (Dysoxylum spectabile), fruits on a female tree.
I'm sorry; I didn't start out to write such a long introduction to what's only a quick observation and a couple of photos.  But it's necessary to set the scene.  Yesterday I went to look at a large population of tītoki in flower at Waiorongomai, near lake Wairarapa.  Here, scattered tītoki trees persist in a grazed paddock on a small area of alluvial river flats, along with some rewarewa and mataī trees.  The lower branches of the tītoki are often within reach, making their study possible.  So I was hoping to check out what their flowers are like, and maybe to observe old fruit on some male trees.

There were obviously two sorts of trees in this population: those that were covered in fruit and those that weren't.  Clearly, last year's flowering had produced a bumper crop.  The trees that weren't bearing fruit were also flowering, and every one that I could reach was a male; the flowers had usually eight stamens and masses of pollen.
Tītoki, male flower.
The fruiting plants weren't flowering, except for one that had a couple of small flowering branchlets within reach.  The flowers on these were different: they had a larger ovary and an obvious red stigma.  But they also had stamens that appeared to be of normal size.  None of the anthers had opened, and I've yet to check (next time I'm near a compound microscope) if they contain pollen.  My expectation is that if they do contain pollen it'll be sterile or maybe have no pores to germinate through, but I could be wrong.  In other words, this observation doesn't really help answer whether tītoki is dioecious or gynodioecious.
Tītoki, female (or maybe hermaphrodite?) flower
Why is it that only the males (with one exception that barely counts) are flowering this year?  It seems counter-productive for males to flower when there are no eggs available to be fertilised.  My hunch is that last year was such a prodigious flowering and fruiting that the female trees have to take a rest; they've been investing their resources in fruit production all through 2012, and that's much less risky than investing in flowers that are only potential fruits.  Males haven't had that costly investment to bear, so they can afford to flower again.  And they have no way of knowing whether the females are flowering or not.

Also, for a male it's a good evolutionary strategy to have sex whenever you can (I always tell my students that biological truth—a consequence of Bateman's Principle—doesn't make it morally or socially acceptable though; we're talking about trees here, not sentient social animals that have to live in a society).  Male flowers and pollen are cheap to produce, so even if most of them might be wasted it's a risk that's worth taking.  This year, pollen from all those male flowers will be competing for the few flowers on that one female tree and next year I'd expect to see very few fruits available in this population.  Unless, that is, some of those male trees can make some fruits, in other words if this population is gynodioecious.
Tītoki, fruit.  The black shiny seed is surrounded by a fleshy aril that attracts birds.
Time will tell, and a revisit is already in my diary for November 2013.  Ideally there'll be a student, interested in making a study of tītoki sex into an honours project, to do the hard yards of all that counting and measuring.

Update, added 26 November 2012.

One of my undergraduate students read the blog above and immediately went to check trees in her mother's garden (in Waikato, North Island).  She sent the photo below, which she correctly described as an inflorescence with mostly male but a few female flowers.  That fits well with my observation that some male trees can set a few fruits, and suggests pretty strongly that tītoki is gynodioecious (we still need good population samples to be sure and to describe the system in detail).
Tītoki inflorescence with male flowers and a few female ones (two are circled)
This observation is also consistent with the comment by Webb et al. (1999) that dioecy in tītoki (probably gynodioecy, we now know) evolved from monoecy, presumably because its relatives are monoecious.  In monoecious populations, all plants are cosexual, and they have separate male and female flowers.  From monoecy, a mutation that suppresses maleness can spread in the population to produce a proportion of female-only plants.  The plants that retain both male and female flowers now reproduce mostly as males because only they can pollinate all the female flowers in the population, their own and all the flowers on the females; that why we call them male now.  Often they come to specialise and some or most may become specialist (constant) males, which seems to be the case in tītoki.  If they all become constant males, the population has moved all the way to dioecy.

You might ask how I can be confident the photo above shows a male with a few female flowers, rather than a female with a few male flowers.  Populations with constant males and inconstant females (females that can produce some pollen) are called androdioecious.  It's an exceedingly rare sexual system and seems to need some special conditions in order to evolve and persist.  There are only a few well-documented examples.  So, given that gynodioecy is vastly commoner, and also that most of the flowers on this branch are male while only a few are female, I think that gynodioecy is the most likely sexual system in tītoki.


Webb, C., Lloyd, D., & Delph, L. (1999). Gender dimorphism in indigenous New Zealand seed plants New Zealand Journal of Botany, 37 (1), 119-130 DOI: 10.1080/0028825X.1999.9512618

Lloyd, D. (1980). Sexual strategies in plants III. A quantitative method for describing the gender of plants New Zealand Journal of Botany, 18 (1), 103-108 DOI: 10.1080/0028825X.1980.10427235

Tuesday, 13 November 2012

Wednesday wildflower: a Cannabis look-alike and a ramble in the bush.

Otari-Wilton's Bush is a patch of forest and an all-native botanical garden in Wellington's suburb Wilton.  It contains most likely the largest bit of mature forest on the Wellington Peninsula, a region that was pretty much all cleared for farming shortly after European settlers arrived.  Much of the forest there is regrowth on old farmland, but some pockets of substantial older podocarp trees still stand.  One is a small group of rimu, Dacrydium cupressinum, on the western side of the valley, matched by another stand nearer the park entrance on the eastern side.
Emergent podocarps over a canopy of tawa (Beilschmiedia tawa, the golden tree in the foreground)
In that western group is one tree that's much larger than all the rest.
The 800-year old rimu at Otari.  The photo doesn't do it justice; that trunk is  nearly 2m diameter.
Maybe it grew faster for some reason, but it's billed as the 800-year old rimu.  If that's true it was a seedling when Māori first arrived, so its age represents all of human history in this land.
Looking up to the crown of the 800-year old rimu.
So to the wildflower/weed.  I've taken a couple of walks at Otari lately, and on the first one I saw this out of the corner of my eye right beside the track.  It brought me up short for a few seconds, until I realised it wasn't Cannabis.
Balm of Gilead, Cedronella canariensis.
Yesterday I went back to see if it was flowering yet, and I had a bit more time to take a good look.  The square stems are a give-away for the family Lamiaceae, and on some old branches I found the remains of last year's fruits, which are in clusters called verticels, again typical of Lamiaceae.  A quick look in the Flora told me that only two Lamiaceae in New Zealand have compound leaves and this matched one of them: Cedronella canariensis, or balm of Gilead.  I'll go back again for photos of the flowers later in the season.
Hīnau, Elaeocarpus dentatus.
Hīnau, Elaeocarpus dentatus, was flowering, and the small white flowers littered the forest floor under the trees.

Pigeonwood, Hedycarya arborea, was also in flower, and the flowers are sweetly scented.
Pigeonwood/porokaiwhiri, Hedycarya arborea, flowers from a male tree above, female below; these ones are not from Otari (scale 1 mm).
It's dioecious (separate male and female trees), and the male flowers were also littering the ground.  The female flowers stay on the trees to become the fruits.  They each have a number of separate carpels (those are their stigmas in the centre of the flower above), so each single female flower forms a cluster of separate fruits.
Old and somewhat shriveled pigeonwood fruits that had fallen to the ground (scale 10 mm).
And here's the beautiful wood pigeon or kererū that disperses those fruits, which take a bit over a year to ripen.  This one was sitting in an introduced broom, Teline stenopetala, in someone's garden near Karori Cemetery, so close to the sidewalk that I could take this photo on my iPhone.  They love young legume leaves, particularly tree lucerne.
Kererū, Hemiphaga novaeseelandiae.

Tuesday, 6 November 2012

Where's the Wednesday Weed?

There hasn't been a clamour of readers who missed the Wednesday Weed today.  Frankly, it's pretty clear from the readership reports I get that Wednesday Weed isn't that popular.  I started it as an easy way of finding some content every week, but to be honest I haven't been very excited by writing those posts, nor apparently have you been very excited by reading them (although the last one got a "cool" and an "interesting").  Plus I've got busier: I have a new part time job that's taking up a fair bit of my botany time, and also a new writing project, both of which I'll say more about later.

So Wednesday Weed might still carry on erratically every other week or so, or it might die a natural death.  I don't intend the blog itself to die though, but posts might not be so frequent.  They might be more inspired, or not.  If you have an opinion, let me know.
Viola odorata, Makara Peak, Wellington
There's plenty more botany to write about.  I'm looking forward to writing more.

Tuesday, 30 October 2012

Wednesday wildflower: Spanish heather

Erica lusitanica is quite invasive, and it seems to do particularly well on clay soils in Wellington.  The epithet lusitanica strictly refers to Portugal, but I guess the species is more widespread than that, so its common name isn't inaccurate.
Erica lusitanica, Messines Road, Karori, Wellington.
They're straggly and untidy plants, yet up close, Erica lusitanica has a pretty hanging flower that starts out pink and fades to white.
Flowers of Spanish heather.

Weed or wildflower, it does at least provide a habitat for the native bag moth.
Bag moth larva, on Erica lusitanica.

Erica is, of course, in the family Ericaceae.  Also in that family: Rhododendron, blueberries, and the native Dracophyllum.

A cultivated Rhododendron, Wellington.
Dracophyllum strictum, cultivated
Dracophyllum scoparium, Campbell Island.

Friday, 26 October 2012

Another Pittosporum

I never cease to be impressed by the flower diversity within New Zealand Pittosporum.  This week I had the chance to photograph P. obcordatum.  The flowers are tiny, and very different in general appearance from the others I've seen.  Like others in the genus, they're sweetly scented, but the scent is rather faint, at least to my nose, and seems strongest at night.
Pittosporum obcordatum
P. obcordatum, the heart-leaved kōhūhū, is quite rare; so it was great news recently that a small population has just been rediscovered on Banks Peninsula.  (Unfortunately the linked article describes it hard to find because it's a cryptic species, but that's not what cryptic species means.  A cryptic species is one that's very hard to distinguish from another related (usually sister) species, where breeding barriers have arisen without morphological changes.  In the case of P. obcordatum, it's the plants that are cryptic, not the species.  Although it's true that other divaricating shrubs can look superficially like P. obcordatum, they have plenty of differences to distinguish them.)

This plant, cultivated on campus at Victoria University, is a female.

Pittosporum obcordatum flowers
For comparison, here are some other pittosporums.

Pittosporum eugenioides.
P. eugenioides is dioecious (has separate male and female plants), and has large clusters of pale yellow flowers.  The males and female flowers are quite different:
Pittosporum eugenioides flowers: female above; male below.
There's a group of species with dark red, almost black, flowers, also sweet-scented at night, like this P. tenuifolium.
Pittosporum tenuifolium flower.
P. tenuifolium is gynodioecious (separate male and female plants, but the males can set some seed even though most of their reproduction is through their pollen).  This one appears to be a male.

The two species I've already illustrated here have narrow pointed petals, and both grow as epiphytes (plants that grow on other plants, but are not parasitic on them).  These are P. kirkii and P. cornifolium.

Finally, a scan of an old slide of P. dallii.  Its flowers are similar to those of P. eugenioides, but its toothed leaves are very different.
Pittosporum dallii.