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of a tree, that the stem is not only a channel for nutrient 

 material, but also a reservoir for reserve material. If by some 

 influence or other the channels for the organic substances become 

 interrupted, it will through this arrangement be possible for the 

 roots and the stem to continue their growth for a long time in 

 quite a normal manner, by bringing the reserve material into 

 action. They will possibly be able to do this sufficiently long until 

 by reason of the tree's activity, the continuity of the channels has 

 been restored and the damage repaired. 



A very simple experiment will give us a clear idea of 

 the functions of the various parts of the stem as channels for the 

 organic and inorganic nutritive substances, and as reservoirs for 

 the reserve material. It is the well-known experiment of 

 girdling the tree. If we interrupt somewhere on the tree the 

 continuity of the cortex and bast, by cutting two circular incisions 

 round the ,stem, some centimetres or so apart, and if we remove the 

 strip of cortex and bast between the two incisions down to the 

 wood, the leaves do not wither (provided that the wood thus 

 exposed is protected against desiccation), the crown continues to 

 grow undisturbed, and produces new organic matter, and there is a 

 continuous increase in the ash-constituents of the crown ; all this 

 proves that the channels in the wood for the transport of water and 

 salts have not been interrupted by this interference. Also the 

 downward transport of the assimilated organic substances from 

 the leaves continues as before. But these organic substances can 

 no longer be conveyed in sufficient quantity as far as the roots, as 

 on account of the girdling the corresponding channels have lost 

 their connection; an accumulation takes place above the ring and 

 there all available reservoirs in the wood, pith, bast and cortex 

 will be crowded with reserve material. As the after-flow of 

 nutritive matter from the leaves into the parts of the tree below the 

 girdle has entirely stopped, the tree will in time be obliged to draw 

 here on all its reserve material in order to supply the matter 

 required for the further growth and sustenance of this part of the 

 stem and for the root-system. While thus in all parts of the stem 

 above the girdle more and more reserve material (for instance 

 starch) is being accumulated, it is on the other hand, noticeable 

 that below the girdle starch gradually disappears from all parts 

 of the stem. Evidently the wood can no longer obtain any 

 appreciable fresh supply of organic substances. 



