THE IMPORTANCE OF THE ROOT-SYSTEM 153 



a given plant. The relative development of the root-system varies widely 

 in different species, and not infrequently an extremely marked development 

 of the root-system is characteristic of plants which do not develop far 

 above the surface of the ground. This is, for example, the case in many 

 mosses and fungi, while, as is well known, the mycelium of a mushroom 

 encompasses a very large area of soil. 



To indicate the marked development the root-system may attain in a short 

 period of time, Nobbe's T comparative observations upon the Pine (Pinus sylvestris, 

 flat root-system) and upon the Fir (Pinus abies, deep root-system) may be 

 mentioned. The measurements were made on one-year-old seedlings grown 

 in sand moistened with nutrient solution. It was found that the total length 

 of the roots formed in one year was, in the pine, 12 metres, in the fir, 2 metres, 

 with a total surface area of 20,515 sq. mm. and 4,139 sq. mm. respectively. The 

 roots of the pine in six months develop throughout a volume of soil, represented 

 by a reversed cone 80 to 90 cm. high, and with almost 2,000 sq. cm. surface. It 

 is hence easy to understand why the pine is able to grow in poor soil, and in spite 

 of the superficial distribution of its roots is nevertheless adequately fixed and 

 anchored to the ground. 



In rapidly growing plants, an even more marked development may be attained 

 during a single summer's vegetative activity. Thus, Nobbe estimates the total 

 length of the root-systems of ripe cereals at from 500 to 600 m. ; S. Clark, for 

 a large water-melon, at 25 kilometres, so that such a plant may easily have directly 

 drained a cubic metre of earth. It may also be mentioned that, in deep and loose 

 sandy soil, the roots of Barley and Mustard penetrate to a depth of i metre, those of 

 the perennial Clover and of Lathyrus sylvestris to from 2 to 3 metres. Schumacher 

 has constructed tables giving the comparative dry weights of the root and shoot 

 systems of different plants 2 . 



External conditions may, as is well known, markedly modify the 

 development of the root-system, and frequently, owing to the impossibility 

 of further penetration, the roots are restricted to particular layers of soil. 

 Thus when a tap-root meets a rock, it branches out over the impenetrable 

 surface and forms a flat root-system. Besides these mechanical agencies, the 

 growth and character of the root-system may be influenced by injuries, and 

 directly or indirectly in a variety of other ways. Moreover, all those 

 correlative influences come into play in the root, which arise from its 

 relationships to the parts above ground, and from the linked and interacting 



1 Nobbe, Versuchsst, 1875, Bd. xvni, p. 279. 



2 Of the literature may be quoted: Fraas, Wurzelleben der Culturpflanzen, 1870; Hellriegel, 

 Jahresb. d. Agr.-Chem., 1864, p. 107; W. Schuhmacher, ibid., 1867, p. 83; Nobbe, Versuchsst., 

 1872, Bd. XV, p. 391 ; Thiel, Landw. Centralbl., 1870, II, p. 249, and the figures from the 'Wand- 

 tafeln' of Nathusius, iv. Sen, 1875; H. Muller, Landw. Jahrb., 1875, IV > P- 399 Resa, Uber die 

 Periode d. Wurzelbildung, 1877; Hoveler, Jahrb. f. \viss. Bot, 1892, Bd. xxiv, p. 296; Frank, 

 Lehrb., 1892, Bd. I, p. 306; Gain, Ann. d. sci. nat., 1894, vii. sen, T. xx, p. 63. 



