1 76 PRINCIPLES OF FARM PRACTICE 



they can develop into plants. A single tumble weed bearing 

 115,000 seeds, a square rod of ground in a garden where 

 potatoes had grown the year before producing 187,884 weeds 

 of eight different kinds, are examples of the great reproductive 

 capacity of weeds, 



A little observation together with the application of simple 

 arithmetic will demonstrate the significance of the large seed 

 production of weeds. For example, an Indian mallow has 

 by actual count about 2480 seeds and occupies 315 square 

 inches of space. If each of the 2480 seeds should produce a 

 plant, there would be that number of plants covering a 

 space of 20 square rods the second year. If each of these 

 plants produced seeds at the same rate there would be, at 

 the end of that season, 6,150,400 seeds. If each of these 

 plants produced a plant the third year, the total area occupied 

 by them would amount to 309 acres. Fortunately, for many 

 reasons, no weed is ever so successful. But the illustration 

 points out clearly the immense possibilities weeds have for 

 multiplying their kind. 



Another important contribution to the success of weeds is 

 the means they have for the dispersal of their seeds. The 

 common weeds not only produce seeds in great numbers, 

 but many of them have very effective ways of scattering 

 them about. When the seeds are light and provided with 

 some means for keeping them suspended, like the seeds of 

 the thistle or dandelion, they may be scattered by the wind. 

 Or the whole plant may be broken off and driven by the wind 

 from place to place, scattering seeds wherever it goes, as in 

 the case of the tumble weed. Some weeds have seeds pro- 

 vided with barbs which are easily caught in the hair or wool 

 of animals, and are thus carried about from place to place, 

 as seeds of the burdock, cocklebur, Spanish needle, sticktight, 



