240 TRANSLOCATION IN PLANTS 



similar tissues. It is difficult to see how solutes, such as 

 nitrogen, for example, may be moving up a stem to a 

 vigorous growing shoot at the apex, passing along the way 

 weak-growing shoots which seem to be suffering from 

 lack of nitrogen, and, although nearer the source of supply 

 than are the apical shoots, yet fail to obtain adequate 

 quantities. Their low content of nitrogen and of other 

 solutes, it would seem, should increase their ability to 

 obtain these solutes when in competition with the apical 

 shoots which supposedly have higher concentrations of 

 these same solutes. That is, the diffusion gradient to 

 these weak side shoots must be steeper than to the vigorous 

 apical shoots, yet they fail to get the materials. A similar 

 anomalous condition may be made out for the roots receiv- 

 ing carbohydrates from the leaves. The lateral roots 

 much nearer the supply may suffer for lack of sugar while 

 roots at a great distance are receiving large supplies. 

 Tensions or pressures in water columns, on the other hand, 

 may be transmitted great distances; therefore inability 

 to compete for water may be more easily explained on the 

 grounds that the osmotic concentration of the side shoots 

 may be low and thus make them incapable of competing 

 with the other tissues for water (Chandler, 1914; Curtis, 

 1920a; Fernald, 1925). 



There is evidence of a similar competition between fruits. 

 For example, there may be several apples on a single 

 spur, all of which, when the terminal blossom is removed, 

 seem to be uniformly distributed so that at first no one 

 fruit seems to have an advantage over any other, either as 

 regards location on the spur, distance from the food source, 

 or attachment to conducting tissue. Yet if one flower is 

 well pollinated or receives pollen which tends to produce 

 more or larger seeds, this fruit may soon become successful 

 in receiving the major part of the foods, and the others, 

 which without the competition might have developed 

 normally, may fail to receive enough food to allow for 

 growth and may actually die or be cut off by an abscission 

 layer (Heinicke, 1917). I have seen no adequate explana- 



