234 ABSORPTION OF LIQUIDS THROUGH ROOTS. 



of the whole plant (all being dried), is less than fifty per cent. 1 

 By comparison of the weights and lengths of average pieces of 

 the roots of barley, it has been found that the whole root-system 

 in a vigorous plant is not far from thirty-seven meters in length ; 

 and that all this could be packed in a small volume of fine soil 

 (about ^ of a cubic foot). 2 



628. The nature of the soil, and especially the amount of 

 moisture and of nutritive matters which it contains, have a 

 marked influence upon the development of the root-system of 

 a plant. Other things being equal, fertility of the soil favors 

 compact branching, as is shown by experiments by Nobbe. 8 



Indian corn was grown for a time in several cylinders con- 

 taining clay soil ; then the earth was carefully washed away and 

 the roots were compared. In the first cylinder the soil had 



1 Amounts as given in Chemische Ackersmann, i. p. 193. 



Roots of winter wheat (in April) 40 per cent. 



" peas (four weeks after planting) ... 44 " 

 " " (at flowering) 24 " 



2 Hellriegel : Hoffmann's Jahresbericht, 1864. 



Nobbe ( Versuchs-Stationen, 1875, p. 279) has given some instructive figures, 

 showing the ratio of the surface above ground to that below in yearling plants 

 of some common species of Conifers grown under similar conditions. Some of 

 his figures are here given. 



a. SURFACE OF ROOTLETS. 



Square millimeters. 



Silver Fir 2,452. 



Norway Spruce 4,139. 



Scotch Pine 20,515. 



b. SURFACE OF THE GREEN PARTS OF THE PLANTS. 



Square millimeters. 



Silver Fir 1,451. 



Norway Spruce . 1,551. 



Scotch Pine 4,304. 



c. RATIO OF PARTS IN THE PLANTS EXAMINED. 



Silver Fir. Norway Spruce Scotch Pine. 



Parts above ground ... 100 : 107 : 297 



Parts below ground ... 100 : 168 : . 837 



d. RATIO OF THE PARTS ABOVE GROUND TO THOSE BELOW. 



Silver Fir 100 : 169 



Norway Spruce 100 : 267 



Scotch Pine 100 : 477 



Versuchs-Statiouen, iv., 1862, pp. 220, 221. 



