6 



THE COCO-NUT 



CHAP. 



But its structure enables it to endure saltiness and 

 dryness which would be fatal to most other plants. 

 Beach soil usually contains no salt, except in such 

 minute quantities as chemical analysis will detect in all 

 soils ; but it sometimes happens as a result of storms 

 that the beach is temporarily filled with sea -water. 

 This would kill any plant with ordinary roots, but does 

 the coco-nut practically no harm at all. 



The same structures enable the coco-nut to withstand 

 drought, not without temporary injury, but without 

 being killed. When any layer of the soil becomes dry 

 enough to injure coco-nut roots in any way, its first 

 effect is to check the growth in length. The hypodermis 

 then approaches closer and closer to the tip, until, if 

 the dryness is severe enough, it reaches the root-cap. 

 In this condition the root is valueless as an absorbing 

 organ; — which does the tree no harm, because an 

 active root could absorb no water from the soil dry 

 enough to cause this condition. When the soil becomes 

 wet again, the roots gradually revive, the cap grows 

 away from the hypodermis, and absorption begins anew. 

 If all the roots ceased to absorb water, the tree would 

 of course be killed, but this cannot happen in any 

 place where coco -nuts ought to be planted. Where 

 coco-nuts become inactive, roots better fitted to absorb 

 water would be killed. 



The numerous little, white, eventually sharp and 

 hard outgrowths scattered along the old coco-nut roots 

 are specialized roots which serve as breathing organs. 

 It is as impossible for air as for water to pass through 

 the hypodermis ; and the internal tissues of old roots 

 would die for want of air, if they were not supplied 

 with it by these breathing organs. 



It has already been remarked that the coco-nut 

 roots have a limited absorbing surface. Even the 

 limited area which looks capable of absorbing actively 

 is sometimes really very inactive. Dead roots will for 

 some time absorb as rapidly as when they are alive ; 

 but if a living root is cut, the end is promptly closed by 



