8i6 



has been repeatedly split longitudinally, and the "lamellae" produced by the 

 tears have a spiral twist which is indicated by dd. The tears are first filled 

 by parenchyma and then the cambial zone, which gradually closes together, 

 deposits wavy layers of new wood («) over the wounds below the unusually 

 strained bark (r), which not infrequently splits here and there in spiral, 

 longitudinal cracks. 



The original upper side, which has become the under side from twisting, 

 shows still greater disturbances. The wood {h'), broken at w and partially 

 split off from the pith, ends in a large knot (m) due to very irregularly 

 curved particles of wood parenchyma. This knot constantly increases in 

 size with continued growth by the formation of new wood (n'). 



It is easy to perceive that the nourishment of the tip of the branch must 

 be disturbed by such an injury to the tissues and that the reserve substances, 

 visible as starch in the parenchymatous overgrowth parts of the edges of the 

 wound, must be enough for the use of the immediately adjacent buds. From 

 what has already been said, it is evident, likewise, that besides this increase 

 in nourishment the buds found directly beneath the place of twisting wall 

 also profit from the increased water pressure. 



The treatment of twisting, as already remarked, is an effective means 

 of retarding the apical growth of a branch to the advantage of the basal buds 

 7, it.'. out, however, causing the uppermost lateral buds, lying below the injury, 

 to sprout at once. The lateral bud immediately below the place of twisting, 

 grows out to a new, vigorous leafy shoot only when the injury to the tissues 

 in the twisting has been so great that the leader can no longer receive the 

 amount of water most necessary to replace that lost by evaporation. It, 

 therefore, dries quickly especially if the maniplation is carried out too early 

 in the year. This result is naturally not desired by the grower. A twisting, 

 carried out too late in the year, would not produce an effect sufficient to 

 prepare the basal buds for fruiting buds, but still would arrest the growth of 

 the branch in length and cause a better ripening of the wood so that it will 

 better withstand the winter. 



In the propagation of quinces by layering, the branch, which is to be 

 layered, is twisted once about its long axis at the place where it is to form 

 roots in the soil. This kind of disturbance is similar to that in the above- 

 mentioned case; the result different inasmuch as the retarded, descending 

 plastic material is used chiefly for the formation of adventitious roots. 



German grape growers in the vicinity of Tiflis are said to twist the 

 stems of the ripe clusters and, thereby, obtain a better wine. The changes, 

 initiated by this treatment, dovetail into one another as follows : the supply 

 of water, from the vine to the cluster, is lessened by the twisting of the 

 stem. Consequently, the evaporation greatly exceeds the supply and the 

 juice of the berries becomes more concentrated. Whatever starch happens 

 to be in the stem is carried as sugar to the berries. They break up and utilize, 

 thereby, a part of the organic acids. The same processes occur in the 

 ripening of cut grapes. 



