K(»OTS 27 



some of the drier parts of ('alifornia wlieat roots liave been 

 known to grow to a deptli of 15 feet and the roots of tlje 

 California poppy to a depth of lo feet. Eoots may penetrate 

 to much greater depths, those of the mesquite of the South- 

 western States and Mexieo scjmetimes descending to reacli 

 water as mucli as (K) feet. It is not difficult to get an idea of 

 the extent of tlie root system of such a plant as Indian corn. 

 Carefully dig away the earth from one side of the plant at a 

 distance of about two feet, keepmg a constant lookout for 

 smaller rootlets. If none are found, extend a trench com- 

 pletety about the plant at the distance already used as a 

 radius. ^lake the trench aljout two feet deep and stand a 

 piece of poultry netting in it, so as to make a circular fence 

 about the roots of the plant. Eun some ■wire stakes crosswise 

 tln'ough the mass of roots, so as to reach across its entire 

 diameter. With a stream of water from a garden hose or with 

 numerous pails of \\'ater -wasli away the earth as completely 

 as possible from the mass of roots and remove the root system 

 entire. It may then be used for illustration in the schoolroom. 

 28. Pull exerted by roots. .Vfter root fibers or the taproots 

 of herljaceous plants have attained their full length, in many 

 kinds of plants a decided shortening of the root takes place. 

 This shortening (jriginates in the cellular portion cif the cor- 

 tex, between its outer layers and the central cylinder of the 

 root, and it may amount to from lo to 25 per cent of the 

 length of the root before contraction. Because the epidermis 

 does not contract, its outer surface often Ijecomes much wrin- 

 kled, especially in the roots of bulbous plants. The shorten- 

 ing of the fibrous r(jots which spring from a taproot holds it 

 firmly in place, as a derrick is held upright by guy ropes. 

 Sometimes, as in the dandelion, the taproot shortens about 

 as fast as the slioit stems A\-hich crown the mot grow upward. 

 In this way the rosette of lea\'es is kept firmly pressed against 

 the ground, or it may even be drawn slightly into the earth. 

 Grass plants on a lawn are injured or destroyed by lieing de- 

 prived of light by the rosette of dandelion or fall dandelion. 



