THE DISPERSION OF SEEDS AND SPORES. 81 



part is provided with several rows of projecting points, 

 and a hispid surface is not uncommon on seeds adapted 

 for wind-transport. On account of its lightness and 

 the ease with which it is wafted, the fruit of 

 dandelion would have difficulty in coming to rest if 

 there were no provision by which it could anchor 

 itself to fixed objects. Just as an aeronaut nearing 

 the earth must throw out his grapple to prevent 

 his balloon being blown about or carried out to sea, 

 so the dandelion-seed requires these projections on 

 its lower part to assist it in alighting on the earth. 

 They are unnecessary in the case of the thistle on 

 account of the readiness with which the pappus 

 becomes detached. Further, the penetrating power 

 of the dandelion-fruit is much greater than we 

 should expect. To be convinced of this one has 

 only to observe what happens when it alights on a 

 tangled mass of dry grass. The seed, kept in its 

 perpendicular position by its parachute, if the air 

 be still, sinks into any opening among the grass- 

 stems, and hangs swinging by its hairs for a time. 

 When the next breeze shakes the mass of hay, the 

 seed slips, but is caught by a grass-stem lower down, 

 where it hangs suspended until another gust shakes 

 the grass, when it slips off and falls down till the 

 pappus-hairs are caught once more. This process is 

 continued, every gust sending the seed farther and 

 farther down into the mass, until at last the soil is 

 reached. Having watched the passage of a dandelion- 

 *eed through a mass of hay in the manner described, 

 the writer can only compare it to a bird hopping 

 among the thick branches of a tree, perching now 

 here and now there, but never striking against any 

 of the boughs or twigs. In its descent the dandelion- 

 seed is greatly assisted by the long stalk which 

 supports the pappus, and by the small projections 

 or barbs on the seed itself. These barbs serve to 

 -anchor the seed and prevent its being lifted up 

 when it has once begun to penetrate ; they enable 

 it to keep every inch it gains. 



