CHAPTER VIII 



WHAT IS A ROOT? 



In popular language the idea "root" implies fundamentality, 

 but, although the rooted plants normally bear their roots as 

 their lowermost parts, there are many plants that have no 

 roots at all and manage quite well without them. The algae — 

 whether microscopic {e.g. diatoms), or big (the seaweeds) — 

 have no true roots, the whole plant living bathed in a nutrient 

 solution. 



There are numerous parasitic plants which utilize other 

 plants' roots. Some, like the sandalwood tree of Southern 

 India, grow apparently independently, but have no true 

 roots of their own and are root-parasites deriving nourishment 

 from the roots of plants of other species growing near. 



Another kind of rootless parasite grows on the ordinary 

 aerial stems of its host without necessarily having any contact 

 with the ground ; parasitic plants of this type rely indirectly on 

 the roots of their hosts — indirectly, because a portion of the 

 host's stem intervenes between parasite and host-roots. 



A root may be defined as an absorptive organ having a 

 characteristic structure and possessing a growing-point pro- 

 tected by a [root-] cap. 



Roots need not be underground; witness the pendant 

 aerial roots in Fig. i and the supporting or buttress-roots of 

 the banyan tree and the stilt-plant {Pandanus sp.). The latter 

 possesses large aerial roots upon which the cap is often 

 distinctly visible to the naked eye.^ 



A root cannot, therefore, be defined as a fundamental part of 



^Excellent pictures of the plant Pandanus sanderae, including a close-up 

 view of the aerial root-cap, are given in the article by John A. Moore, in the 

 Missouri Botanical Garden Bulletin, 1933, 21, No. 10. 



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