40 INTERRELATIONS OF PLANTS AND ANIMALS 



best fitted to scatter their seeds, or to place their fruits contain- 

 ing seeds some Httle distance from the parent plants, are the ones 

 which will spread most rapidly. A plant, in order to advance into 

 new territory, must first get its seeds there. Plants which are best 

 fitted to do this are the most widely distributed on the earth. 



Seeds and fruits transported by the wind : 1, milkweed ; 2, ash ; 3, maple ; 4, dan- 

 delion ; 5, clematis ; 6, elm ; 7, basswood ; 8, thistle. 



How Seeds and Fruits are scattered. — Seed dispersal is accom- 

 plished in many different ways. Some plants produce enormous 

 numbers of seeds which may or may not have special devices to 

 aid in their scattering. Most weeds are thus started in '^ pastures 

 new." Some prolific plants, like the milkweed, have seeds with a 

 little tuft of hairlike down which allows them to be carried by the 

 wind. Others, as the omnipresent dandelion, have their fruits 



Fruits transported by animals: 1, beggar-tick; 2, tick trefoil; 3, Spanish needle i 

 4, cocklebm- ; 5, sand bur ; 6, small flowered agrimony. 



provided with a similar structure, the pappus. Some plants, as 

 the burdock and cocklebur, have fruits provided with tiny hooks 

 which stick to the hair of animals, thus securing transportation. 

 Most fleshy fruits contain indigestible seeds, so that when the 

 fruits are eaten by animals the seeds are passed off from the 

 body unharmed and may, if favorably placed, grow. Nuts of 

 various kinds are often carried off by squirrels, buried, and for- 



