112 



General Botany 



In many of the grasses and grass-like plants, rootstocks develop 

 rapidly in all directions, sending up erect branches at short in- 

 tervals. The rootstocks and their accompanying roots soon 

 become mixed with those of adjoining plants, finally forming a 

 closely interwoven mat which is the '' turf " of lawns and mead- 

 ows. Turf-forming grasses are often of great value for holding 

 in place the soil of embankments, dikes, and levees. In these 

 plants the rootstocks are mainly useful in spreading or extending 

 the plant. Bermuda grass and Johnson grass are troublesome 

 weeds in the Southern states because of their extensive rootstock 

 systems. On the other hand, this same feature makes some 

 plants of great use to man. The sand-reed grass (Ammophila) 

 has been planted extensively in Europe and in America to hold 



drifting sand in place and to pre- 

 vent the sand from invading towns 

 and cultivated fields. This grass 

 may also be used as a soil binder in 

 starting forests in sandy places. 



In plants like the May apple, 

 Solomon's seal, and yellow water 

 lily, the rootstock 

 not only causes 

 the plant to 

 spread, but it 

 also accumulates 

 a part of the food 

 manufactured 

 each season and 

 thus serves as a 

 storage organ. 

 j.E.wea.er The uudergrouud 



Fig. 6i. Vertical section of a gravel slide, showing dogbane Stem 01 aspara- 



(Apocynum) with underground stems (rootstocks) connecting „^^ jg ^ StOrage 

 the several shoots, and the much-branched root system. Section 



divided into one-foot squares. Organ, and aS it 



