6 



lateral root usually takes its place and continues its growth, in 

 the direction of the original tap-root. A root-system with a 

 tap-root has thus a distinct main axis and usually penetrates to 

 a considerable depth in the soil. A strong tap-root is deve- 

 loped by many of our forest trees, e.g. Teak (Tectona grandis) , 

 Sissoo, (Dalbergia Sissoo) and Anjan (Hardwickia binata). 

 Such a root of Sissoo, or Anjan, may attain a length of six 

 feet in the first year. 



In many plants, however, such as grasses and their allies, the 

 first root sent out by the seedling dies off after a short time, or 

 does not develop vigorously, and stronger roots then spring 

 from the base of the stem above the primary root. These, 

 although they often arise above the ground in the air, may 

 ultimately penetrate the soil and branch there, and in many 

 plants the entire root-system consists of such adventitious 

 roots. They may be well seen in the sugarcane. For illustra- 

 tions, see Plate I, Figs. 3 and 4. 



The question whether a plant develops a strong tap-root, 

 or a superficial root-system, is of great practical importance. 

 Plants with the same type of root-system compete with each 

 other in the same layers of soil for water and raw food 

 materials. A tree with a long tap-root, like the Sissoo, is thus 

 a good nurse to protect tea-bushes from the effects of frost, 

 the roots of these two plants not interfering with each other, 

 while the superficial roots of Toon (Cedrela Toona) and other 

 species, which are often planted in avenues near field crops, are 

 injurious to the latter. 



The extent of the root-system developed by a plant depends 

 on the amount of green foliage produced by the shoot. The 

 greater the latter, the larger and more vigorous is the former. 

 Plants with leaves floating in water usually have a small total 

 area of leaf surface, while water also is plentiful close at hand, 

 and such plants usually possess a small root-system. If, on the 

 other hand, we collect all the roots of a large forest tree, such 

 as the Sal, and place them end to end they would probably 

 cover a distance of several miles. 



Development 8. In the case of many of our 



of Root forest trees the development of the root to a great extent 



itf*A/%nri<vQ 1*1 



precedes that of the shoot. The plant, as it were, has to 

 make sure of its foundations below ground before pro- 

 ceeding with the superstructure and the development of the 

 shoot above ground may often be quite insignificant for several 

 years, during the early life of the seedling. Fig. 1, Plate I, 

 shows the strong well-developed tap-root of a young seedling of 



