VITALITY OF THE 'SEQUOIA GIGANTEA DUDLEY 37 



It is the latter word we use in this paper. The effort of an injured 

 tree is not one to re-establish organic connection of the new tissue with the 

 old, injured surface below, but wholly one to complete and re-establish, by 

 extension, the broken circle of growth the broken annual rings to round 

 out the tree again to its full circumference, to establish roots below, sup- 

 porting and sap-conducting tissue above. Fortunately for the tree, it has 

 no nervous system connected with delicately organized "nerve centers" ; no 

 circulatory system extending to every point of its surface and connected with 

 and controlled by a small uncertain organ deep within the body. The 

 heart-wood of a Big Tree is imperishable while the tree stands and long 

 after it falls, unless attacked by fire. In the words of the foreman of the 

 logging camp, "nothing hurts the heart of a redwood nothing; it's always 

 sound." Moreover, it is completely independent of the living zones outside 

 of it, although joined cell by cell with the living tissue. Its cells have 

 ceased to grow or change, and the living juices of the plant have ceased 

 to flow in them. From the point of view of life, whatever tissue in a tree 

 has ceased to grow in every sense, has ceased to be vitally useful. Only 

 that tissue which is in the process of building is living, is a vital part of 

 the great organism, and this life must exist in a complete cylinder forming 

 the outer tissues of the trunk; a circle constantly, and in the case of a 

 Big Tree, indefinitely widening. If the circle is broken, apparently all the 

 energies of life and growth are directed toward closing it again, not toward 

 any useless vivification of the dead cells of the wound below. The burned 

 surface is dead tissue, not differing essentially from that of the tree's heart- 

 wood, and the healing of the latter is only incidental to the tree's supreme 

 effort at the extension of its living tissue over the wound in order to re- 

 unite the margins of the zone that should have remained inviolate and un- 

 broken. 



The increase of the tree is rhythmical, as we have seen, accompanying 

 the sun and the seasons. The Spring after a wound has occurred, the tree 

 begins its effort toward healing by the formation of a layer of wood and 

 bark along all margins of the burned area. This is repeated the second 

 year, a layer of new wood tissue being superimposed upon that of the 

 previous year along the burned margins. These layers next the wound are 

 much thicker than the ordinary ones, the ring for the same year on the 

 side of the tree opposite the burn being often correspondingly thinner and 

 more attenuated. This process continues with each returning season, and 

 the new tissue reaching inwards from all margins of the injury takes on 

 the form of solid folds of wood growing uniformly broader on each side, 

 the black char narrower, year by year. There is no organic union, however, 



