632 WEED FLORA OF IOWA 



The dissemination of weeds is not unlike that of other plants. 

 Weeds are commonly recognized as plants out of place, plants 

 which are detrimental to the growth of crops or otherwise in- 

 jurious. "Wihile ash or maple seeds are not usually placed in this 

 category ; if, in their seedling sba-ge they monopolize a piece of soil, 

 for example a lawn newly planted with grass, absorbing the nutri- 

 ment and crowding the plants desired in this location, these in- 

 vaders have earned for themselves the title "weed." The epithet 



Pig. 495A P!g. 495B 



Fig. 495. Seeds and fruit scattered by the wind. A. Basswood (.Tilia ameri- 

 cana), a light bract to which is attached a stalk bearing the fruits. B. 

 Milkweed XAsclepias syriaca) pod and seeds. 



(Drawings by Ada Hayden.) 



"weed" brings to mind the obnoxious characters of the plants so 

 designated, yet weeds have just as respectable lineage as the palm, 

 oUve, lily or laurel, and in their systematic relationships they 

 show by their structure that they are members of the first families 

 of the plant kingdom. Thus the notable rose family, which serves 

 the world with the apple, the plum, the cherry, the quince, the 

 peach and the pear, claims among its numbers the aggressive little 

 cinquefoil {Potentilla fruticosa), an invader of pastures and tilled 

 lands, the thorny prairie rose {Rosa pratincola) and the prickly 

 black raspberry {Buhus occidentalis) , which without invitation en- 

 trench themselves upon the territory and contend with the agri- 

 culturist as to what shall occupy the soil. Families such as the 



