65 



writer very nearly succeeded in an attempt to force this new 

 growth to produce fibres at right angles to the normal direction : 

 i. e., they were made to bend more than 80 degrees. 



The fact that new iibres can, if necessary, be formed at such 

 a great angle from the normal is of very great advantage to the 

 chestnut in the process of healing over scars made, for example, 

 by cutting out diseased spots in the bark. As food is conveyed 

 through a plant in very dilute watery solutions, it is necessary 

 that a great amount of sap be circulated or conveyed to a point 

 where any considerable amount of food is demanded. If the 

 tubes which primarily convey sap should be severed, as when a 

 diseased spot has been cut out of the bark, the free transfer of 

 sap is at most seasons of the year immediately reduced to a mini- 

 mum in the severed or "dead ends" of these sap conducting tubes, 

 which from the point of view of circulation, now hold about 

 the same relation to the uninjured tubes that the stagnant arm 

 of a river does to the main river. 



So far as the actual food is concerned, it is obvious that the 

 amount of sap necessary to supply the requisite food cannot 

 reach the upper and lower edges of a scar by means of the dead 

 ends of the conducting tubes as readily and rapidly as at the 

 edges where there is a continuous stream of sap passing along 

 the uninjured tubes. 



Oftentimes just below a broad scar which reaches to the wood, 

 and less often above it, a triangular piece of bark will die. This 

 is due directly or indirectly to the inability or great difficulty 

 that the sap has in reaching these places. In order to preclude 

 the possibility of the bark dying back either above or below a 

 scar, and thus furnishing favorable shelters for insects, the top 

 and bottom of the scar should be pointed instead of allowed to 

 remain abrupt or rounded. Under ordinary conditions it takes 

 no longer for a scar six inches long and an inch wide to heal 

 over completely than it does for one an inch long and an inch 

 wide, simply because the healing over depends almost entirely 

 upon the growth at the sides of the scar. As I have already in- 

 timated, all cuts should be made with instruments that are kept 

 very sharp. 



(2). Mycelium in the wood. 



