35° 



NATURE-STUDY 



are covered with spines, recurved hooks, etc. to catch into 

 the fur of animals and the garments of people. Plants with 

 burs are found abundantly where animals go, in the past- 

 ures, along the fences and roadsides, around bams. There 



we find cocklebur, bur- 

 dock, sandbur, pitch- 

 forks, beggar's-lice, tick- 

 trefoil, etc. Even the 

 barbs or beards of 

 grasses and grains act 

 Hke burs. This is well 

 seen in barley and in 

 the squirrel -tail grass. 

 In the latter each grain 

 is provided with several 

 long, slender, barbed 

 awns. When the head 

 is ripe it breaks up into 

 the separate grains. 

 Passing animals catch 

 the barbed awns and the 

 seed is scattered. The 

 wind, however, may 

 blow these light grains, the barbs acting as sails. Along 

 almost every country lane and the roadways leading from 

 the cities into the country we may see these bur weeds migrat- 

 ing. The cattle, sheep, horses, dogs, and men passing along 

 assist them on the way. Burs have learned the trick of steal- 

 ing rides. 



Man has carried the seeds of cultivated plants from one 

 end of the globe to the other. Wherever he goes he takes 



Fig. 145. Cocklebur. 



