ROOTS AND ROOT-STOCKS OF WEEDS 



651 



Underground 



rhizomes of common 

 sepium). 

 (Photographed by Stevens.) 



Morning-glory ( Convolvulus 



Roots. 



Adventitious buds are produced at indefinite points along the 

 roots and from them stems and plants develop. A number of our 

 noxious weeds are propagated by these running or creeping roots, 

 such as: milkweed (Asclepias cornuti), bindweed (Convolvulus 

 arvensis), sheep sorrel {Bumex acetosella), Indian hemp {Apocy- 

 num cammabinum) , perennial rag'wteed {Amhrosia psilostacJiifa) , 

 pasture thistle [Cirsium undulatum). 



The weeds mentioned above are comparatively shallow rooted. 

 A few weeds are propagated by buds which come from deep vertical 

 roots. Among them we find the following : horse nettle {Solarium 

 carolinense), ground cherry (Physalis sp.), Canada thistle {Girsiwn 

 arvense). 



Undebgeotjnd Stems ob Rhizomes. 



These underground stems are usually found at a short distance 

 beneath the surface. Along these stems are found nodes with leaf 

 scales at definite intervals. From these nodes roots develop which 

 penetrate the soil and leafy stems which develop above ground. 

 Some of the weeds so propagated are as follows: quack grass 



