Dandelion seeds are caught on an inflorescence of the 'Spiralis' cultivar of Juncus effusus.
From Wikipedia (http://en.wikipedia.org/wiki/Juncus_effusus):
Soft Rush (Juncus effusus) is a member of the Juncus genus found growing in wet areassuch as the purple moor-grass and rush pastures and fen-meadow plant associations in the United Kingdom. It is native to most continents.
It grows in large clumps about 1.5 meters (5 feet) tall at the water’s edge along streams and ditches, but can be invasive anywhere with moist soil. It is commonly found growing in humus-rich areas like marshes, ditches, fens, and beaver dams.
The stems are smooth cylinders with light pith filling. The yellowish inflorescence appears to emerge from one side of the stem about 20 cm from the top. In fact the stem ends there; the top part is the bract, that continues with only a slight colour-band marking it from the stem. The lower leaves are reduced to a brown sheath at the bottom of the stem.