785 



Even in the poplars a complete circle of strong green branches grows 

 up around the edge of the cut wood body. Such an "eruption of shoots" 

 degenerates, as a rule, after a few years because it is not able in its place of 

 production between bark and wood to form new roots which can reach the 

 soil. If soil reaches the base of these shoots by being covered or by prema- 

 ture decay of parts of the bark, the shoots can free themselves from 

 the nutritive trunk by growing roots and form long lived, independent 

 individuals. 



The ability to produce new shoots from the tree stump, very differently 

 developed in different tree genera and very rarely in conifers, does not 

 always depend on the formation of adventitious buds but also on the awak- 

 ening of dormant eyes as in conifers. In this, however, the hard cortex of 

 the stump often hinders further development. 



If such a subsequent development of shoots is expected and desired, as 

 in forestration or in parks, the trees must be cut down as deep as possible 

 in order to give the new shoots a good chance to root. 



The custom, not infrequently found, of renewing tree plantations by 

 leaving stumps one meter high, should be given up absolutely. The new 

 shoots developing on such stumps are, on an average, much weaker and are 

 often surpassed by shoots at the surface of the soil. 



Overgrowth Processes in Year Old Branches. 



In our cultivated trees, the necessity arises of cutting back the tops in 

 order to prune the foliage shoots and thus favor the fruit buds, or in trans- 

 planting to bring the top into balance with the injured root system. The 

 pruning affects principally the year old growth, and is done either in the fall 

 or early spring. Consequently, a considerable time passes before the 

 processes of closing the wounds begin through new formation of tissue. In 

 this it is found not infrequently that such young growth dies back for a 

 short distance from the cut surface. 



In Fig. 179 is shown the tip of a year old cherry branch which has 

 dried back some distance from the cut surface. Fig. 180 shows the same 

 branch cut through longitudinally ; .y to / is the original cut surface ; t is the 

 boundary layer, back to which the twig has died ; a, a swelling frequently 

 found in such cases. Fig. 181 shows the anatomical structure. In it, s to / 

 is the plane of the cut, a h, the last peripheral particle of the old wood of the 

 cut surface; a r, the old bark with its outer normal cork layers (k). Of 

 this bark, the tissue indicated by T has dried back and, in fact, the tissue 

 near the hard bast cords (b) dies the furthest downward; the bast cord is 

 also dead and together with the outer cork layers of the bark, which also are 

 but little shriveled, projects from the discolored parenchyma. The cut 

 surface is, therefore, uneven and rough. 



The next process which sets in, after injury and after the upper bark 

 tissue has died, consists in the cutting off of the dead from the healthy tissue, 

 by means of the formation of a cork zone (k', k"). The cork zone is devel- 



