Thanks everyone. I really didn't realise orchid flowers could be so big, my large Phalenopsis are about 6cm and my Dendrobium maybe 4cm.
I first read this book years ago when I was a teen and I didn't know what an orchid was then let alone any of the varieties. When I have re-read it now I could actually imagine the flowers being described far better, especially when I looked up the Oncidium ornithorhynchum on Google.