[Chap. XXVII GENERAL REGIONS AND PROCESSES IN STEMS 269 



the ground and below all lateral branches, an adequate translocation of 

 sugar from leaves to roots no longer occurs in most species of plants, but 

 movement of water in the xylem from roots to leaves still continues. In 

 trees the roots and base of the trunk below the girdle may contain enough 

 food to survive for a year or two after the girdle is made. Death and 

 decay of the roots are ultimately followed by the death of the plant above 

 the girdle as a result of desiccation. 



In most species of plants apical dominance of the tops is sufficient to 

 inhibit the growth of sprouts from the base of the trunk. When girdling 

 annuls this apical dominance sprouts may grow from the roots or base of 

 the trunk of girdled trees, as they usually do when a live tree is suddenlv 

 cut down. Likewise, if there are lateral branches below the girdle, or if 

 apical dominance fails to inhibit the growth of sprouts from the base of 

 the tree, the tree may survive for many years. 



If the bark is not completely removed, or if the girdle is very narrow, 

 new phloem may develop from the cambium before accumulated food in 

 the roots is exhausted, and the tree may survive. When the girdled area 

 does not become drv and is otherwise protected by grafting wax, a 

 new cambium and phloem may develop across the girdle while the roots 

 are still alive. Advantage is sometimes taken of this fact in horticultural 

 practice. Branches, or even the main trunk, of fruit trees are girdled to 

 bring about internal conditions favorable to the formation of flowers 

 and fruits without killing the tree. Girdling prevents not only the down- 

 ward translocation of sugar, but also the upward translocation of the 

 amino acids and proteins made in the roots. 



Girdling is often incorrectly done in that so much of the younger 

 xvlem is cut awav with the bark that the movement of water to the 

 leaves is greatlv diminished. In such cases the leaves wilt within a few 

 davs, and the top above the girdle dies of desiccation before the roots 

 starve to death. With the death of the top its apical dominance disap- 

 pears, and sprouts may grow from the roots or from the base of the 

 trunk. Apparent exceptions to these statements of course need further 

 analysis than given here. 



Herbaceous steins. If stems of herbaceous plants, such as those of 

 common weeds, garden plants, and crop plants, are cut and dissected, 

 as directed above for woody stems, soft tissues and vascular bundles are 

 readily discernible, and in some species a hard outer rind is evident. 

 Here again differences in color and texture are indicative of different 

 kinds of tissues definitelv arranged. In stems of dicots the cortex and 



