Completing the petals

Last time, I was just concentrating on the largest of the wood avens, to demonstrate shading with split stitch.  I've now done the rest of the flowers' petals in the same way.

As most of the flowers are pretty small, I only worked a band of stitches in the lightest shade, 0104, on the next-largest flower, at the bottom of the sheet.  For the others (apart from the very little one, which is just in the darker shade), I did the first band in one strand of each colour; in the second-largest flower, I also worked a band of that, as the transitional stage:

I then finished the rest of the petals, using the darker of the two shades, 0105:

That's all the petals completed, but you can hardly have failed to notice a large space in the centre of each flower.  What's going to go there?  That's next!