64 REGENERATION 



stem (with the exception of the apical end) is in water the roots 

 form in all the nodes and do not wilt since they have enough water 

 (Fig. 49). Shoots formed in this case only at the apex. When 

 the whole stem is in water, with the exception of the basal end, 

 shoots may be formed in all the nodes (Fig. 50) especially in old 

 stems. Stems suspended in moist air in the same position form 

 shoots only at the apical end (Fig. 51). It is obvious that the 

 limited amount of water available in a stem suspended in moist 

 air (even if it dips with one end into water) is a contributory cause 

 to the polar character of regeneration in the stem, since when the 

 stem is submersed in water the formation of roots and shoots is 

 not confined to the two poles of the stem. 



It may be stated incidentally that in the leaves formed on a 

 stem under water the ratio of width to length is smaller than in 

 leaves formed in air. 



