More Heterostyly

Purple Loosestrife, Lythrum salicaria.   Central stigma.  On the River Medway near Hartlake Bridge, 25 July 2014.

Back in May 2013 I wrote a post on heterostyly, the way that some flowers have more than one distinct configuration of their anthers and stigmas.  The usual example is the Primrose, which had two configurations known as pin-eyed and thrum-eyed.  Check that old post for examples.

I said then that the Purple Loosestrife is unusual in that it has three configurations.  I had intended to find examples that year, but I never did.  However, recently I visited a spot where there were lots of specimens, and I found examples of all three.  At the top of this post you can see a flower with both long and short anthers, and a mid-length stigma.

It's also clear that the different lengths of stamens have differently coloured pollen, yellow on the short ones and a dark green on the longer ones.  If I find out more about that I will write it up.

Purple Loosestrife, Lythrum salicaria.   Short stigma.  On the River Medway near Hartlake Bridge, 25 July 2014.

It's not so easy to show the short stigma because it tends to be hidden in the tube at the base of the flower, but here you can see it, and especially in the lower flower, it's clear that it is positioned below the shorter yellow stamens.

I only got one rather scrappy shot of the third configuration ...

  Purple Loosestrife, Lythrum salicaria.   Long stigma.  On the River Medway near Hartlake Bridge, 25 July 2014.

But at least it is very clear that this stigma is mugh longer than both groups of stamens.

So I was pleased with this result!  I found a paper on line that said experimental results showed that all the pollen can fertilise any plant, but pollinating within the same flower resulted in lower fertility.

Not all visiting insects can be regarded as potential cross-pollinators.

Hoverfly, Sphaerophoria species, female, on Purple Loosestrife, Lythrum salicaria.
On the River Medway, 25 July 2014.

This little hoverfly, a Sphaerophoria, is delicate enough to be able to pick up single grains of pollen from the petals, and it will also lick the anthers, but it  never goes inside the flower looking for nectar and always stays quite clean.