Little Arrows, Little Arrows
The dreaded Acaena, not the Leapy Lee variety!
This is part of the burr produced by the plant Acaena novae-zelandiae (buzzy or biddy-bids).
Unlike other burrs which have hooks, this plant has barbed arrows. Once they get into your clothing, there is only one way they can move - inwards! Then it is not long before they are attacking flesh - very irritating.
Fortunately, these plants are not particularly common around here (Hobart, Tasmania) - unlike my experiences on South Georgia with the related species Acaena magellanica where it was ubiquitous and agressive.
This particular image is of a young flowerhead where the arrows are still pink and relatively soft. As they age, they become stiffer and a golden brown colour.
These little arrows are best avoided . . .
. . . but if you prefer the Leapy Lee version, here is a link: http://www.youtube.com/watch?v=xZIkM3Uu6gI