By this time you can guess why.
When the seeds are ripe and the silky plumes all nicely formed that stem stands up!
It stands straight up and looks over the tops of the grasses. Then the green bracts on the outside turn back, and the silky tufts spread out and pull themselves free from the remains of the tiny flowers which have withered and are no longer yellow. They do not fall off when the flower first closes, but make a little cap to protect the growing akenes, and when these get ready to open out the cap is pushed off by them.
Opening out and pushing off the cap.
The hollow stem stands up, and its lovely silky head of plumed akenes shines in the sunlight.
There is nothing much prettier in the plant world than this head of fairy dandelion akenes all ready to fly away.
They stand and shine until a breeze comes along that is strong enough to dislodge them, then all in a moment they are off sailing through the air.
The parent plant is not sorry to have them go, for this is what it has worked so hard to accomplish; and as they float away, if it thinks at all, it no doubt hopes that each little shining wanderer will alight at last in a beautiful home of its own with plenty of space and sunlight and food for its growth.