223 



.^ 



in plant-physiology is the outcome of the squirrels' labour. In 

 the examples referred to the damage had been very severe; long 

 strips of bark had been removed, so that in one ease a considerable 

 portion of the trunk appeared as a pole of bare wood with islands 

 of bark upon it. Branches of the stem inserted within some of 

 these islands were still living, and bore healthy foliage, although 

 their isolation by the removal of the bark from around the islands 

 had taken place more than two years previously. 

 ; Some further specimens injured in a similar manner have 

 recently been received from the same donor. In one of these the 

 ' bark had been ringed, and the tree had eventually died, but it was 

 found by examining the annual lings that the part above the 

 wound had lived for at least four years after the ringing-operation. 

 Other specimens examined showed from three to five years' growth 

 above the ring-gap.* 



In these cases the wood exposed by the injury is perfectly bare, 

 and of course no new., layers of wood have been formed on its 

 surface, as the stripping of the bark involves the removal or death 

 of the cambial layer. The outer layers of the wood exposed to the 

 air soon become dry and useless for conduction, hence it is clear 

 that the older layers of wood must be capable of continued fairly 

 rapid transference upwards of water coming from the roots, as 

 evidenced by the continued life of the parts above the ring-gap. 

 In the case of the specimens previously examined, though some 

 of the branches remained fresh, the water supply had proved 

 insufficient to keep the tops of the trees healthy. 



The effect of ringing differs in different kind of trees. Yarious 

 experiments have been made, and a study of the results of the 

 operation proved useful in the early days of plant physiology in 

 leading to a knowledge of the route of conduction of water and of 

 elaborated f ood-substances in plants. Experiments in ringing 

 were made by Malpighi and Hay, of whom the latterf mentions 

 that a holly tree lived for several years after a ring of bark of a 

 hand^s breadth had been removed irom the stem so as to leave the 

 wood bare. Since this early observation numerous experiments 

 have been made on several kinds of trees, and form two classes, 

 viz. : — (1) bark-ringing, z.6., the stripping off of a ring of bark as 

 in the cases mentioned above; and (2) wood-ringing, i.e., making 

 an annular cut into the stem through both bark and part of the 

 wood. 



Bark=riiiging. — The effects of bark-ringing depend upon the 

 interruption of the bark and the exposure of the wood. The 

 break in the continuity of the bark prevents the normal conduction 

 of elaborated food-substances (albuminous and carbohydrate) from 

 the parts above the ring-gap to those below, since these bodies are 

 ordinarily conveyed through the barkj (or more precisely the 



^^ M» I - - ■■— ■■ - - - _ -- ^ ^ - ^ -| ■ I ^ ^ ■ ■ - ■ - Bill 1,1 



* By this is meant the annular gap in the bark, made by the operation 

 of bark -ringing. 



t Ray, Hist. Plant., T. 1, p, 9. 



J Any conduction of food-substances that may take place through the 

 wood in the downward direction would be against the transpiration current, 

 and might be expected to be slight. That it is slight or non-existent is 

 suggested by the fact that growth in thickness of the stem practically ceases 

 below the ring-gap. 



