54 



FRUITS AND THEIR USES 



The cocklebur. Note the curved 

 hooks. 



some of our worst weeds in this way. The burdock and clotbur are 

 familiar examples. In both the mass of little hooks is all that re- 



mains of an involucre. Thus the whole 



fruit cluster may be carried about and 

 seeds scattered. In many of the Com- 

 posites, as in the cockleburs and beg- 

 gar's-ticks, the fruits are provided with 

 strong curved projections which bear 

 many smaller hooklike barbs. 



Pappus. Probably the most im- 

 portant adaptations for dispersal of seeds are those by which the 

 fruit is fitted for dispersal by the wind. That much-loved and 

 much-hated weed, the dandelion, gives us an example of a plant in 

 which the whole fruit is carried by the wind. The parachute, or 

 pappus, is an outgrowth of the ovary wall. Many other fruits, 

 notably that of the 

 Canada thistle, are 

 provided with the pap- 

 pus as a means of 

 getting away. In the 

 milkweed the seeds 

 have developed a silky 

 outgrowth which may 

 carry them for miles. 

 In New York city the 

 air is sometimes full of 

 the down from these 

 seeds, which is brought 

 from far over the 

 meadows of New Jer- 

 sey by the prevailing 

 westerly wind. 



Dehiscent Fruits and 

 how they Scatter Speds. 

 One of the many meth- 

 ods of getting rid of seeds 

 is seen in dry fruits. These simply split to allow of the escape of the 

 seeds. Examples of common fruits that split open (dehiscent) are seen 



Dandelion heads ; the middle one a mass of ripe 

 fruits ready to be scattered by the wind. Photo- 

 graphed by Overton. 



