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here has grown small and hair-like, and acts as a sail or 

 wing for the light little fruit. Thus the wind catches 

 the seeds when ripe and carries them away to every part 

 of the field. In the simpler plants of the dandelion kind 

 there are only a few of these silky hairs seated perpen- 

 dicularly on the summit of the fruit, and the subsidiary 

 devices for dispersion are far less perfect. But in the 

 dandelion itself, which is a very highly adapted type 

 all these common weeds always are, and that is what 

 makes them so common the top of the fruit grows out 

 into a long beak, on which the hairs spread laterally in a 

 circle, so as to present the largest possibly surface to the 

 favoring breeze. Even in the dandelion, however, the 

 hairs themselves are straight and simple ; in its near rela- 

 tive, John-go-to-bed-at-noon, the hairs are much longer, 

 and are subdivided into feathery branches on either side, 

 which make an interlacing parachute even better adapted 

 for driving before the wind than that of its more familiar 

 kinsmen. 



The reason why plants take all this trouble to get their 

 seeds dispersed is a simple one, and yet it might not 

 immediately strike everybody. Why should they not let 

 them drop out upon the ground just underneath their own 

 branches ? For the very same reason that the farmer 

 does not crop the same land with corn or turnips ten 

 years running. The plants had unconsciously discovered 

 rotation of crops ages before the agriculturists conscious- 

 ly hit upon it. A weed cannot grow over and over 

 again in the same place, any more than flax or horse- 

 beans ; it soon uses up the soil, which must then lie fal- 

 low a little, or else bear some less exhausting plant that 

 is to say, some plant that does not drain it of the same 

 materials as its last occupant. Hence those wild things 

 which happened to show any tendency toward dispersive 



