144 TEANSACTIONS OF THE ILLINOIS 



moved in kind from that which animates animals and quickens the 

 physiological forces of man. In the soil this property of roots causes 

 them to go in the way of least resistance, to bend or tend to bend 

 from the solid mass to the crevice, from the stone to the friable 

 earth. 



It has been shown also that the tip of the root is similarly sen- 

 sitive to moisture - — the bending being toward the moist side. Or- 

 chids — air plants of tropical regions — have long roots, which 

 usually hang vertically downward in moist air; but when these 

 plants are placed upon blocks of wood in our green-houses the roots 

 often follow the damp wood to the lower end, then turn abruptly 

 across the bottom of the block, and reaching the other side even 

 bend upward and cling to the damp surface until they reach the top, 

 and, so continuing, wind themselves again and again about the fre- 

 quently watered wood. So roots are known to find drain tile and 

 other reservoirs of water, and to largely develop there. 



In this connection it may be stated that roots develop much 

 more abundantly in rich soil, and generally in the presence of nutri- 

 tious substances, than in the opposite condition of things. In poor 

 soils roots are long and straggling, with few active branches and 

 branchlets. 



The enormous force exerted by roots ought not to be passed 

 without notice. It is surprising how some roots penetrate hard soils 

 or force themselves through the hard substances. The roots of some 

 grasses and sedges pierce potatoes through and through. When 

 once entered the swelling roots exert an incredible lateral pressure. 

 Great stones are split in twain; walls of masonry are crowded out 

 of place, heavy flag-stones are tilted from position, and ponderous 

 forest trees are lifted bodily by the increase in diameter of large 

 horizontal roots. 



Fiinctmi of Roots — All agricultural plants require to be stead- 

 fastly held in position, and this holding is one of the indispensable 

 ofiices of roots. Their intimate connection with the particles of the 

 soil, their ramifications and the angular directions of branches, and, 

 above all, their prodigious length and number render roots exceed- 

 ingly efiicient in this respect. Thousands of newly transplanted 

 trees die from the want of secure anchorage; he who plants wisely 

 attends carefully to this, as well as to other, points. Roots of bien- 

 nial and perennial plants serve also as storehouses of food, the nu- 

 trient matters elaborated during the first year being passed to the 

 cells of the roots, whence they may be withdrawn the following 

 spring. 



But the great business of roots is to absorb water and certain 

 other matters from the soil. It is especially for this purpose that 

 they have their peculiar structure and wonderful development. And 

 since it is usual in nature that the means by which results are ac- 

 complished compare closely with the work required, we may feel 



