12 WEEDS OF THE FARM AND GARDEN 



roots are conical. Common quack grass, wood sage, and 

 peppermint produce numerous horizontal rootstocks that 

 are found close to the surface of the ground, 75 per cent 

 of the rootstocks being" found within four inches of the 

 surface. From the nodes there arise numerous small 

 fibrous roots. 



The roots of many perennial plants, like Canada thistle, 

 morning-glory, horse nettle, and milkweed, spread exten- 

 sively through the ground. The root of a common milk- 

 weed was traced by Mr. Garner and Mr. Lyle Clapper for 

 a distance of 14 feet through the soil. 



Dr. Byron D. Halsted, who made a study of the roots of 

 various weeds, comments as follows concerning the char- 

 acter of roots : "By means of the root system most plants 

 become anchored to the soil ; therefore, other things re- 

 maining the same, among those species that live from 

 year to year, the size of the root becomes an index of the 

 persistency and pestiferousness of the plant." Then he 

 comments upon the length of roots of a great many 

 different weeds, stating that the common dandelion 

 (Taraxacum officinale) had a root an inch in diameter and 

 fifteen inches in length, but the writer has found a root 

 of the dandelion more than four feet in length. It should 

 be remembered also that in many cases when the root is 

 injured near the top that a multiple root development 

 follows. The burdock and dock frequently produce 

 numerous roots when the plants are injured, although 

 ordinarily these roots are straight and produce a single 

 thick fleshy root. The characters of roots sometimes 

 differ very materially in closely related species of plants. 

 The common sour dock has a straight fleshy root, 

 whereas the smooth or peach-leaf dock produces a num- 

 ber of branched roots, making it rather difficult to ex- 

 terminate. 



The following tables give the depth of roots, and area 

 covered by some of the common weeds. These figures 



