Beard or no beard?

I learnt something new about dog roses today. It's a very old riddle, originally in Latin, which has been translated thus: 

On a summer's day, in sultry weather
Five Brethren were born together.
Two had beards and two had none
And the other had but half a one.

It refers to the five sepals of this particular flower, two of which are whiskered on both sides, two of which are smooth-sided and the remaining one is whiskered on one side only.

Sepals are what enclose the flower bud like a tight wrapping until it's ready to bloom, they then open to release the petals but remain splayed around the flower stem.
If you examine the sepals behind  an open dog rose it becomes clear what the rhyme refers to.

In the image above you can see three of the flower's sepals, two have smooth edges the middle one is 'whiskered'. The bud to the left is still tightly enclosed by its sepals.  It seems that the uneven disposition of the 'whiskers' may serve wrap the bud securely.

The extra shows the back of a rose with its variously-whiskered sepals.

The riddle is thought to have been invented by mediaeval monks as they tended their monastery gardens. Anyone interested in learning more might like to read the short article here (go to page 4) which is actually quite fascinating and has alternative attempts at translating the  original Latin verse.