76 A TEXT-BOOK OF GRASSES 
cum (L.) Karst., 7’. officinale Weber.) is a familiar exam- 
ple of this group. Cutting off the plant below the crown 
does not destrdy the dandelion, as adventitious buds may be 
produced on the cut root from which new shoots develop. 
102. Perennial weeds with creeping rhizomes or creep- 
ing propagating roots include the most troublesome 
species, as the widely spreading rhizomes or roots are 
difficult to remove completely from the soil. Portions of 
the rhizomes remaining in the soil may give rise to new 
shoots. Creeping propagating roots are to be distinguished 
from creeping rhizomes or rootstocks, which are modified 
stems. Creeping roots possess no scales or modified 
leaves, but have the structure of roots. They will, how- 
ever, if they are propagating roots, have the power to 
produce adventitious buds. Some weeds with creeping 
roots are bindweed (Convolvulus arvensis L.) and sheep 
sorrel (Rumex Acetosella L.). None of the weedy grasses 
possesses creeping roots. Creeping rhizomes indicate 
their character as modified stems by the presence of scales 
that mark the nodes at regular intervals. To this group 
belong the white morning-glory (Convolvulus Sepium L.), 
the nut-grass (Cyperus rotundus L.) and Johnson-grass. 
103. Weedy grasses.—Grasses may be of all degrees 
of weediness. Many species that are classed as weeds are 
harmless since they are found only in waste places or 
along roadsides. Among these are goose-grass, crowfoot- 
grass and old-witch grass. Only a few of the more impor- 
tant weedy grasses will be mentioned here. 
104. Annual weeds.—In the eastern states the com- 
mon species are green foxtail, yellow foxtail, and upon 
sandy land, the sandbur. Here, and more especially in 
the South, crab-grass is a common weed. All these yield 
readily to cultivation. Crab-grass is particularly trouble- 
